materials Article

Building Energy Storage Panel Based on Paraffin/Expanded Perlite: Preparation and Thermal Performance Study Xiangfei Kong 1, *, Yuliang Zhong 1 , Xian Rong 2 , Chunhua Min 1 and Chengying Qi 1 1 2

*

School of Energy and Environmental Engineering, Hebei University of Technology, Tianjin 300401, China; [email protected] (Y.Z.); [email protected] (C.M.); [email protected] (C.Q.) School of Civil Engineering, Hebei University of Technology, Tianjin 300401, China; [email protected] Correspondence: [email protected]; Tel./Fax: +86-22-6043-5279

Academic Editor: Luisa F. Cabeza Received: 1 December 2015; Accepted: 18 January 2016; Published: 25 January 2016

Abstract: This study is focused on the preparation and performance of a building energy storage panel (BESP). The BESP was fabricated through a mold pressing method based on phase change material particle (PCMP), which was prepared in two steps: vacuum absorption and surface film coating. Firstly, phase change material (PCM) was incorporated into expanded perlite (EP) through a vacuum absorption method to obtain composite PCM; secondly, the composite PCM was immersed into the mixture of colloidal silica and organic acrylate, and then it was taken out and dried naturally. A series of experiments, including differential scanning calorimeter (DSC), scanning electron microscope (SEM), best matching test, and durability test, have been conducted to characterize and analyze the thermophysical property and reliability of PCMP. Additionally, the thermal performance of BESP was studied through a dynamic thermal property test. The results have showed that: (1) the surface film coating procedure can effectively solve the leakage problem of composite phase change material prepared by vacuum impregnation; (2) the optimum adsorption ratio for paraffin and EP was 52.5:47.5 in mass fraction, and the PCMP has good thermal properties, stability, and durability; and (3) in the process of dynamic thermal performance test, BESP have low temperature variation, significant temperature lagging, and large heat storage ability, which indicated the potential of BESP in the application of building energy efficiency. Keywords: building energy storage panel; phase change material particle; vacuum absorption; surface film coating; expanded perlite; paraffin

1. Introduction With the improvement of economic conditions and peoples’ living standards, peoples’ requirements for the thermal environment inside the building have gradually improved [1–3], resulting in energy consumption rapidly growing for the air conditioning and heating supply [4,5]. Phase change material (PCM) incorporated with the building envelope for thermal storage has received increasing attention in the building energy efficiency field [6,7]. On the one hand, PCM can increase the thermal inertia of the building envelope and reduce heat loss through latent heat storing to achieve building energy efficiency; on the other hand, PCM can decrease the temperature fluctuation in the building by repeating its thermal absorbing and releasing circulation, for enhancing indoor thermal comfort. In early research, a sample method was adopted to study the PCM used in buildings, which refers to the liquid PCMs or solid PCM powders that were directly incorporated into the building envelope materials, such as gypsum, mortar and concrete, etc. [8,9]. However, PCM was very easy to leak out from building materials, resulting in operational difficulty in practical application [8]. For improving Materials 2016, 9, 70; doi:10.3390/ma9020070

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incorporation of PCM into building materials, the method of liquid PCM immersion into shaped building materials (bricks, gypsum boards and concrete slabs, etc.) has emerged [10–13]. Although the immersion method has improved the performance of the direct incorporation method, the leakage of liquid PCM still occurred, especially after repeated cycles [8]. In addition, leakage of PCM can reduce the total amount of PCM used in building, and the mechanical property of construction can also be affected by the interaction between leaked PCM and cement mortars [14]. Therefore, to overcome these issues, composite PCMs with encapsulation techniques, inclusive of microencapsulated PCM and form-stable PCM, have been extensively and deeply studied in recent years. Microencapsulated PCM can finish the melting and freezing cycle of PCM in the capsule shell with no liquid PCM oozing [8] and, thus, it was generally incorporated into concrete, cement mortar, and gypsum board [15–18]. However, some incompatibility problems with the building materials have also been experienced. Excessive microencapsulated PCMs can lead to an intensity of building materials decreased and, meanwhile, insufficient microencapsulated PCMs will not achieve the desired effect of thermal storage [19]. Additionally, several capsule shells of microencapsulated PCMs were destroyed in the blending process into concrete or cement mortar, resulting in their stability reducing [20]. The form-stable PCM, which was obtained through PCMs incorporated into supporting materials, has been attracting increasing attention due to its ability to keep the shape of PCM stabilized in the phase change process [8,21]. The greatest advantage of form-stable PCM is that it does not need additional containers or shells to encapsulate PCM and thus form-stable PCM can be incorporated into the building envelope with a simple and convenient implementation. Considering these good points, many form-stable PCMs have been prepared and analyzed in the last two decades. The components and fabrication method of the form-stable PCM are the important research area in literatures. The organic PCMs such as paraffin, fatty acids and eutectic mixtures of binary PCMs are always used for form-stable PCMs due to their stable thermal performance, high latent heat, and low sub-cooling [22–24]. Building materials with a large amount of micropores in their internal structures, such as vermiculite, expanded perlite, diatomite, gypsum, and natural clay, etc., were generally adopted to be the supporting material in form-stable PCM [25–28]. Thus, the vacuum adsorption was used in incorporation of PCM into supporting material for achieving a better stabilization compared to that of the direct immersion method [14,27,29]. Another research area focused on is the property improvement of form-stable PCM. For improving heat conductivity, addition agents inclusive of expanded graphite, metal powder, and carbon fiber have been mixed in the preparations [30,31] and, thus, the heat transfer performance of form-stable PCM was enhanced. Although the stability and thermal property have been studied and improved in the recent research, an undesired problem of melted PCM leaking from porous materials has been reported. In [32], the fact that paraffin leaked from the PCM cement composites has been presented and, thus, to overcome this shortcoming, the surfaces of diatomite/paraffin composites were modified by using a kind of coating material (Aerosil® R202, Evonik, Herne, Germany) with high surface energy. Li et al. have addressed the leakage of form-stable PCM has reduced the thermal performance and workability of cementitious PCM composites, and they proposed that modifiers of hydrophobic fumed silica and precipitated silica using into form-stable PCM can prevent the leakage problem [33]. Ramakrishnan et al. have also mentioned the leakage problem for composite PCMs, and in their research a kind of hydrophobic coated expanded perlite (EP) was used to prevent the leakage problem [14]. Sun and Wu have attempted to define the maximum leakage that was acceptable for form-stable PCM using in buildings [34]. Kheradmand et al. have indicated that the issue concerning PCMs leakage from porous material should be focused on and, thus, they proposed that PCM composites (impregnated/encased PCMs in lightweight aggregates) were surface coated with waterproofing solutions to solve the liquid PCM leakage problem [35]. From the above research, it can be concluded that the composite PCMs supported by porous materials require a protection to prevent melted PCM leaking.

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Materials 2016, 9, 70 3 of 16 composite PCM particle was prepared though vacuum absorption method to achieve the maximum  PCM absorption capacity. It should be noted that with no other building materials mixing, such as  cements and mortars, the energy storage panel was developed by composite PCM particles and a  In this study, a surface protective layer obtained by composite PCM particle immersing into the mixture of silica and organic acrylate, so as tothe  solve the leakage problem. The and,  composite PCM small  amount  of colloidal adhesives,  which  can  enhance  percentage  of  PCMs  thus,  achieve  a  particle was prepared though vacuum absorption method to achieve the maximum PCM absorption considerable thermal storage capacity. Additionally, related property studies of PCM particle and  capacity. It should be noted that with no other building materials mixing, such as cements and mortars, energy storage panels for the building application were also conducted. 

the energy storage panel was developed by composite PCM particles and a small amount of adhesives, which can enhance the percentage of PCMs and, thus, achieve a considerable thermal storage capacity. 2. Experimental  Additionally, related property studies of PCM particle and energy storage panels for the building application were also conducted.

2.1. Phase Change Material  2. Experimental

Paraffin  is  an  organic  PCM  with  the  stable  performance  of  non‐toxic  and  non‐corrosive  and  2.1. Phase Change Material low cost. 25# paraffin purchased from Sinopec Nanyang LTD (Nanyang, China) was chosen to use  Paraffin is an organic PCM with the stable performance of non-toxic and non-corrosive and low in this study. As shown in Figure 1, the phase change point is 25.8 °C, which is within the range of  cost. 25# paraffin purchased from Sinopec Nanyang LTD (Nanyang, China) was chosen to use in this indoor thermal comfort [36].The latent heat is 107.6 J/g, which is also suitable for building energy  study. As shown in Figure 1, the phase change point is 25.8 ˝ C, which is within the range of indoor storage [37].  thermal comfort [36].The latent heat is 107.6 J/g, which is also suitable for building energy storage [37].

  Figure 1. Differential scanning calorimeter (DSC) curves of 25# paraffin. Figure 1. Differential scanning calorimeter (DSC) curves of 25# paraffin. 

2.2. Preparation of PCMP

2.2. Preparation of PCMP 

2.2.1. Support Material

2.2.1. Support Material  The support material in building energy storage panel (BESP) not only should support the phase material particles also encapsulate PCMs. (BESP)  The expanded perlite, a common The change support  material  in (PCMPs), building but energy  storage  panel  not  only  should  support  the  building material, has certain mechanical performance and has been widely used in the building of phase  change  material  particles  (PCMPs),  but  also  encapsulate  PCMs.  The  expanded  perlite,    thermal insulation [38,39]. Additionally, it can firmly contain PCM by its porous properties. Therefore, a common building material, has certain mechanical performance and has been widely used in the  expanded perlite with particle size distribution of 4–6 mm was used to be the support material in this building study, of  thermal  insulation  Additionally,  it  can  and the specific physical[38,39].  parameters are shown in Table 1. firmly  contain  PCM  by  its  porous  properties. Therefore, expanded perlite with particle size distribution of 4–6 mm was used to be the  Table 1. Property of expanded perlite. support material in this study, and the specific physical parameters are shown in Table 1.  Material

EP

Table 1. Property of expanded perlite.  400 Weight (kg/m3 ) Thermal conductivity (W/(m¨ K)) 0.05 2.35 RegenerativeMaterial coefficient (W/m2 ¨ K) 3)  2 ¨ K) 2.45 Heat transfer coefficient (W/m Weight (kg/m Specific heat (W¨ h/(kg¨ K)) 1.17 Thermal conductivity (W/(m∙K))  2.68 BET surface area (m2 /g)

EP 400  0.05  2 Regenerative coefficient (W/m ∙K)  2.35  Heat transfer coefficient (W/m2∙K)  2.45  Specific heat (W∙h/(kg∙K))  1.17  2 BET surface area (m /g)  2.68 

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2.2.2. Preparation Process of PCMP Materials 2016, 9, 70 

4 of 16  The preparation of PCMP in this study included two stages: the PCM was absorbed into support material by vacuum absorption method, in order to obtain the composite phase change material; and material; and then, PCMP was prepared by composite phase change material coated with film, so as  then, PCMP was prepared by composite phase change material coated with film, so as to guarantee no to guarantee no leakage for PCMP.  leakage for PCMP. Figure  2  has  shown  the  process  of  prepared  PCMP  by  using  vacuum  absorption,  and  the  Figure 2 has shown the process of prepared PCMP by using vacuum absorption, and the detailed detailed procedure was presented as the following.  procedure was presented as the following. 1. Expanded perlite has been dried in a drying cabinet for 5 h, at first. Then, a certain quality  1. Expanded perlite has been dried in a drying cabinet for 5 h, at first. Then, a certain quality of of paraffin, expanded perlite and magnetic particles were put into a suction bottle, and then  paraffin, expanded perlite and magnetic particles were put into a suction bottle, and then the the vacuum pump was started, in order to keep the internal pressure of the suction bottle to  vacuum pump was started, in order to keep the internal pressure of the suction bottle to be be 0.5 MPa.  0.5 MPa. 2. 30 min later, the heating magnetic stirrer was opened with the heating temperature of 80 °C.  ˝ C. Then, 2. 30 min later, the heating magnetic was opened the evacuated  heating temperature of 80 2  Then,  the  inside  pressure  of  stirrer suction  flask  was with further  to  0.01  MPa.  h  later,    the the vacuum absorption process was finished.  inside pressure of suction flask was further evacuated to 0.01 MPa. 2 h later, the vacuum process was finished. 3.absorption The  vacuum  pump  was  closed  and,  meanwhile,  the  piston  of  the  flask  was  removed.    3. TheThe paraffin can be further absorbed into the micropores of expand perlite, especially the  vacuum pump was closed and, meanwhile, the piston of the flask was removed. The paraffin canresidual  be further absorbed the micropores of expand perlite, especially the residual paraffin in paraffin  in  into the  surface  of  expanded  perlite,  under  the  driving  force  which  was  the generated from the pressure change (from 0.01 MPa to atmospheric pressure).  surface of expanded perlite, under the driving force which was generated from the pressure (from 0.01 MPa to atmospheric pressure). 4.change 1 h later, the heating magnetic stirrer was closed, and then paraffin/expanded perlite in the  4. 1 h suction  later, the heating was closed,the  and then paraffin/expanded perlitechange  in the flask  were magnetic naturally stirrer cooled.  Finally,  preparation  of  composite  phase  suction flask were naturally cooled. Finally, the preparation of composite phase change material material  was  accomplished,  and  the  real  composite  phase  change  material  can  be  seen  in  wasFigure 3a.  accomplished, and the real composite phase change material can be seen in Figure 3a.

Theoretically, encapsulated inin  thethe  support material after vacuum adsorption for the Theoretically, PCM PCM can can bebe  encapsulated  support  material  after  vacuum  adsorption  for  capillary force and surface tension with the micropores in the support material. However, a small the  capillary  force  and  surface  tension  with  the  micropores  in  the  support  material.  However,    amount of liquid PCMs can be leaked out from support material, due to the volume change in phase a small amount of liquid PCMs can be leaked out from support material, due to the volume change  transition process [14,32–34]. Additionally, some kindssome  of PCMs have a peculiar smell, such assmell,  fatty in  phase  transition  process  [14,32–34].  Additionally,  kinds  of  PCMs  have  a  peculiar  acids. Tofatty  overcome shortcomings, process of filma coating prepared composite phase such  as  acids. these To  overcome  these ashortcomings,  process for of  the film  coating  for  the  prepared  change material has been studied. composite phase change material has been studied.  When the vacuum absorption process is finished, the second stage-coating film process can be When the vacuum absorption process is finished, the second stage‐coating film process can be  started. The composite phase change material was immersed into the mixer of colloidal silica and started. The composite phase change material was immersed into the mixer of colloidal silica and  organic acrylic. After 30 min, the composite phase change material was taken out from the mixture organic acrylic. After 30 min, the composite phase change material was taken out from the mixture  and naturally naturally dried. dried. Finally, Finally,  a  thin  be  created  around  the  surface  of  composite  phase  and a thin filmfilm  can can  be created around the surface of composite phase change change  material  to  the overcome  leakage  and  the  preparation  PCMP  was  material to overcome leakage the  problem, and problem,  the preparation of PCMP was alsoof  completed. The also  real completed. The real PCMPs were showed in Figure 3b.  PCMPs were showed in Figure 3b.

  Figure 2. Vacuum absorption experimental sketch.  Figure 2. Vacuum absorption experimental sketch.

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(a) 

(b) 

  Figure  3.  Pictures  composite  phase change material (PCM)  Figure 3. Pictures of  of composite phase change material (PCM) without  without surface  surface film  film coating  coating (a)  (a) and  and (a)  (b)  phase change material particle (PCMP) (b).  phase change material particle (PCMP) (b). Figure  3.  Pictures  of  composite  phase change material (PCM)  without  surface  film  coating  (a)  and 

2.3. Preparation of BESP  phase change material particle (PCMP) (b).  2.3. Preparation of BESP The studied BESP was constituted of PCMP and adhesive (styrene acrylic emulsion in this study)  2.3. Preparation of BESP  The studied BESP was constituted of PCMP and adhesive (styrene acrylic emulsion in this study) with  a  certain  proportion  of  the  two  materials.  The  mold  pressing  method  was  conducted  in  the  with a certain proportion of the two materials. The mold pressing method was conducted in the BESP The studied BESP was constituted of PCMP and adhesive (styrene acrylic emulsion in this study)  BESP preparation, as shown in Figure 4, and the specific steps are as follows:  preparation, as shown in Figure 4, and specificThe  steps arepressing  as follows: with  a  certain  proportion  of  the  two the materials.  mold  method  was  conducted  in  the  1. PCMP and styrene acrylic emulsion were mixed and stirred in the mass ratio of 8:1.  BESP preparation, as shown in Figure 4, and the specific steps are as follows:  1. PCMP and styrene acrylic emulsion were mixed and stirred in the mass ratio of 8:1. 2. When they were mixed well, they were put into the mold that has the retaining flanges.  1. PCMP and styrene acrylic emulsion were mixed and stirred in the mass ratio of 8:1.  2. When they were mixed well, they were put into the mold that has the retaining flanges. 3. The mixture of PCMP and styrene acrylic emulsion were distributed evenly and pressed with  2. When they were mixed well, they were put into the mold that has the retaining flanges.  3. The mixture of PCMP and styrene acrylic emulsion were distributed evenly and pressed with the the pressure of 4 MPa to maintain the compactness.  3. The mixture of PCMP and styrene acrylic emulsion were distributed evenly and pressed with  pressure of 4 MPa to maintain the compactness. 4. After a time period of 12 h, the shape of BESP was stabilized.  the pressure of 4 MPa to maintain the compactness.  4. Finally, BESP was successfully prepared, and was fetched out from the disassembled mold.  After a time period of 12 h, the shape of BESP was stabilized. 4. After a time period of 12 h, the shape of BESP was stabilized.  5. 5. Finally, BESP was successfully prepared, and was fetched out from the disassembled mold. 5. Finally, BESP was successfully prepared, and was fetched out from the disassembled mold.  In  Figure  5,  the  finished  BESP  sample  has  been  presented.  It  can  be  seen  that  BESP  has  a  In  Figure  the  finished  sample  presented.  It  can  be  seen  BESP  a  In Figure 5, the5, finished BESPBESP  sample has has  beenbeen  presented. It can be seen thatthat  BESP hashas  a smooth smooth appearance and ready for use in the building envelope.  smooth appearance and ready for use in the building envelope.  appearance and ready for use in the building envelope.

  Figure 4. Schematic diagram of the fabricating process of the energy storage panel.  Figure 4. Schematic diagram of the fabricating process of the energy storage panel.

Figure 4. Schematic diagram of the fabricating process of the energy storage panel. 

 

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  Figure 5. Energy storage panel sample. Figure 5. Energy storage panel sample. 

2.4. Leakage Test 2.4. Leakage Test    Before the leakage test, a series of PCMPs with different proportions of paraffin and expanded

Before the leakage test, a series of PCMPs with different proportions of paraffin and expanded  perlite were prepared. Then, a diffusion-oozing circle test proposed by Ma et al. [40] was used to perlite  were  prepared.  Then,  a  diffusion‐oozing  circle  test  proposed  by  Ma  et  al.  [40]  was  used  to  conduct the leakage test. The diffusion-oozing circle test is that a standard circle written in a filter conduct the leakage test. The diffusion‐oozing circle test is that a standard circle written in a filter  paper was used to determine the leak performance of the composite PCMs. In this test, the diameter paper was used to determine the leak performance of the composite PCMs. In this test, the diameter  of standard circle was to be 30 mm, and a certain quality of PCMPs was uniformly distributed into of standard circle was to be 30 mm, and a certain quality of PCMPs was uniformly distributed into  the standard circle. Then, in order to ensure the paraffin completely melted, PCMPs were kept at the  standard circle.  Then, in  order  to aensure  the When paraffin  completely  melted,  PCMPs  were  kept  at  the temperature of 50 ˝ C for 5 h by flat heater. finishing the heating process, PCMPs were removed from the filter paper, and the leakage circle of melted paraffin was measured. the temperature of 50 °C for 5 h by a flat heater. When finishing the heating process, PCMPs were  removed from the filter paper, and the leakage circle of melted paraffin was measured.  2.5. Thermal Property Test

High thermal property is an important index for PCM application research [27]. In this study, 2.5. Thermal Property Test    the researched BESP thermal properties included the phase change point, latent heat, and heat High thermal property is an important index for PCM application research [27]. In this study,  conductivity coefficient. The phase change point and latent heat were determined by differential the  researched  BESP  thermal  properties model, included  the  phase  change  point,  and  heat  scanning calorimeter (DSC) (DSC2910 TA Instruments Company, Newlatent  Castle,heat,  DE, USA). conductivity  coefficient.  The  change  and from latent  heat ofwere  by  differential  The test sample of DSC wasphase  0.5 mg, which point  was taken inside BESP.determined  Within a nitrogen (N2 ) ˝ C at a heating scanning  calorimeter (DSC)  TA  Instruments  Company,  New rate Castle,  DE,  USA).  atmosphere, the sample has(DSC2910  been tested model,  by DSC over the range of 0–50 of 5 ˝ C/min. In addition, the accuracy of DSC was ˘0.1 ˝ C and ˘1% for temperature and latent heat, respectively. 2)  The test sample of DSC was 0.5 mg, which was taken from inside of BESP. Within a nitrogen (N A heat conductivity coefficient of BESP wasby  measured by a bench-top conductivity instrument atmosphere,  the  sample  has  been  tested  DSC  over  the  range thermal of  0–50  °C  at  a  heating  rate  of    (HFM436 model, NETZSCH, Selb, Germany) with the accuracy of ˘3%. 5  °C/min.  In addition,  the accuracy  of DSC  was ±0.1  °C  and ±1%  for  temperature  and  latent  heat, 

respectively.  A  heat Observation conductivity  coefficient  of  BESP  2.6. Microstructure and Mechanical Property Tests was  measured  by  a  bench‐top  thermal  conductivity instrument (HFM436 model, NETZSCH, Selb, Germany) with the accuracy of±3%. 

Scanning electron microscope (SEM) was used to observe the microstructure of BESP and expanded perlite. The SEM pictures were used to analyze the performance of paraffin incorporated 2.6. Microstructure Observation and Mechanical Property Tests  into micropores of expanded perlite. Scanning  electron  microscope  (SEM)  was  used  to  observe  of  BESP  and  In mechanical property test, the compressive strength of BESP the  was microstructure  measured by an electronic universal testing machine (WDW-10, Wintures Testing Technology Co. Ltd., Jinan, China), and the expanded perlite. The SEM pictures were used to analyze the performance of paraffin incorporated  accuracy of this test machine was 20 N. Additionally, the test was started when the styrene acrylic into micropores of expanded perlite.  emulsion in BESP was completely solidified. In mechanical property test, the compressive strength of BESP was measured by an electronic 

universal testing machine (WDW‐10, Wintures Testing Technology Co. Ltd., Jinan, China), and the  accuracy of this test machine was 20 N. Additionally, the test was started when the styrene acrylic  emulsion in BESP was completely solidified.  2.7. Durability Test  The  melting–freezing  cycle  was  speedily  completed  by  circulating  a  water  bath  for  the  test  sample.  1000  cycles  were  conducted,  and  the  sample  after  the  last  cycle  was  tested  by  DSC  for 

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2.7. Durability Test The melting–freezing cycle was speedily completed by circulating a water bath for the test sample. 1000 cycles were conducted, and the sample after the last cycle was tested by DSC for comparison with it before the cycles. The data of the two DSC tests were compared, in order to determine the durability of BESP in long-time using. 2.8. Dynamic Thermal Performance Test A dynamic thermal performance test, as shown in the Figure 6, was conducted for verifying the BESP dynamic thermal behavior, which refers to the temperature response and heat-storage characteristics. The thermal parameters were monitored by T-type thermocouples for temperatures and thermal flux sensors for heat flows, respectively. The data were recorded by an Agilent data logger and transmitted to a personal computer terminal. The detailed information of instruments was listed in Table 2. Table 2. Instrument details. Instruments Thermocouple Thermal flux sensor Data logger Thermostatic waterbath Hot/cold plate PC terminal

Model

Quantity

T-type WYP Agilent 34972A Julabo F-12 Manufactured by aluminum sheet; 20 ˆ 20 ˆ 10 mm3 Lenovo ThinkStation P300

Accuracy ˝C

Operation Range

3 2 1 2

ď˘0.4 ď5% ď0.0041% ď˘0.03 ˝ C

´35–100 ˝ C ´20–100 ˝ C ´20–100 ˝ C

2

-

-

1

-

-

Two hollow plates connected with two thermostatic water baths were used as dynamic heat and cold sources, respectively, through adjusting the water temperatures of the water baths. A sandwich structure (hot plate-sample-cold plate) was adopted in the testing part, and it was encapsulated with rubber insulation cotton to avoid the external disturbance. Two thermocouples and thermal flux sensors were installed on the hot/cold surfaces of testing sample, respectively, and a thermocouple was embedded into the internal of samples. Additionally, the adjacent surfaces in the sandwich structure were smeared with thermal silicone grease to eliminate the influence of thermal contact resistances and ensure the measurement accuracy of heat across the sample [41]. The dynamic operating temperature of the hot plate was inputted according to the Equation (1), which has been obtained through 24-h typical meteorological data [42] of China cold-zone fitting with time and, meanwhile, the temperature of the cold plate was maintained to be 26 ˝ C. The fitting curve was showed in Figure 7. T “ 11.7643 ` 16.6662τ ´ 13.1061τ2 ` 4.9722τ3 ´ 1.0097τ4 ` 0.1251τ5 ´0.0098τ6 ` 0.0005τ7 ´ 1.4847e´0.005 τ8 ` 2.4704e´0.007 τ9 ´ 1.7251e´0.009 τ10

(1)

where T and τ represent temperature (˝ C) and time (h), respectively; R-squared value is 0.99746. It should be noted that the temperature (T) in Equation (1) was the solar-air temperature, which has been ascertained through Equation (2): T “ Tair `

aI αout

(2)

where Tair and I are the outdoor air temperature (˝ C) and solar radiation intensity (W/m2 ), respectively; meanwhile, a and αout represent absorption factor of solar radiation convective and heat transfer coefficient (W/(m2 ¨ ˝ C)), respectively. Both Tair and I are obtained from the typical meteorological data in [42].

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Figure 6.Schematic diagram of dynamic thermal performance test.  Figure 6. Schematic diagram of dynamic thermal performance test. Figure 6.Schematic diagram of dynamic thermal performance test. 

 

 

Figure 7.Fitting curve of typical meteorological data and time.  Figure 7. Fitting curve of typical meteorological data and time. Figure 7.Fitting curve of typical meteorological data and time. 

3. Results and Discussion  3. Results and Discussion 3. Results and Discussion  3.1. Leakage Analysis  3.1. Leakage Analysis According  to  [40],  η  can  be  used  to  characteristic  the  leakage  in  diffusion‐oozing  circle  test.    3.1. Leakage Analysis  According to [40], η can be used to characteristic the leakage in diffusion-oozing circle test. It is It is obtained by Equation 3:  According  to  [40],  η  obtained by Equation (3):can  be  used  to  characteristic  the  leakage  in  diffusion‐oozing  circle  test.    DDLK It is obtained by Equation 3:  100%   ηη“ LK ˆ100% (3) (3) DDSD

DSD

where D is the diameter of circle, and subscripts LK  and SD represent the leakage circle and standard η  of LK 100% where  D  is  the  diameter  of  circle,  and  subscripts  of  LK  and  SD  represent  the  leakage  circle  and  (3) circle, respectively. DSD standard circle, respectively.  Seven samples with different proportions of paraffin and EP have been tested for leakage, and the where  D Seven samples with different proportions of paraffin and EP have been tested for leakage, and  is  the listed diameter  of 3.circle,  subscripts  LK  and  SD severe represent  the mass leakage  circle  and  results were in Table It can and  be found that the of  leakage become with the percentage the  results  were  listed  in  Table  3.  It  can  be  found  that  the  leakage  become  severe  with  the  mass  standard circle, respectively.  rising of paraffin and η is also increased. A certain value of η, 115% [34], is considered to be the percentage rising of paraffin and η is also increased. A certain value of η, 115% [34], is considered to  maximum value, in which the leakage of porous composite PCM is acceptable and safe. Thereby, the Seven samples with different proportions of paraffin and EP have been tested for leakage, and  be  the  maximum  value,  in  which  the  leakage  of  porous  composite  PCM  is  acceptable  and  safe.  paraffin percentage wt % confirmed to be thethe  most appropriate adsorbing the  results  were  listed of in 52.5 Table  3.  was It  can  be  found  that  leakage  become  severe  capacity with  the ofmass  Thereby, the paraffin percentage of 52.5 wt % was confirmed to be the most appropriate adsorbing  composite PCM in this study. percentage rising of paraffin and η is also increased. A certain value of η, 115% [34], is considered to  capacity of composite PCM in this study.  The last sample (Sample 8) is the  the composite PCM with coating film.PCM  Both PCMs in surfaceand  and safe.  be  the  maximum  value,  in  which  leakage  of  porous  composite  is  acceptable  The last sample (Sample 8) is the composite PCM with coating film. Both PCMs in surface and  porous EP were encapsulated into the film in Sample 8, so the leakage of melted PCM was avoided, Thereby, the paraffin percentage of 52.5 wt % was confirmed to be the most appropriate adsorbing  porous EP were encapsulated into the film in Sample 8, so the leakage of melted PCM was avoided,  capacity of composite PCM in this study.  and  the  comparison  of  leakage  performance  for  Sample  5  and  Sample  8  was  shown  in  Figure  8.   

The last sample (Sample 8) is the composite PCM with coating film. Both PCMs in surface and  porous EP were encapsulated into the film in Sample 8, so the leakage of melted PCM was avoided,  and  the  comparison  of  leakage  performance  for  Sample  5  and  Sample  8  was  shown  in  Figure  8.   

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and the comparison of leakage performance for Sample 5 and Sample 8 was shown in Figure 8. The The  result  that  η  value  of  Sample  8  was  100%  has  indicated  the  high‐quality  effect  of  the  coating  result that η value of Sample 8 was 100% has indicated the high-quality effect of the coating film film  in  leakage  prevention.  A  similar  method  to  prevent  the  leakage  problem  of  liquid  PCM  was  in leakage prevention. A similar method to prevent the leakage problem of liquid PCM was also also reported in [35], in which several waterproofing materials, such as Sikalastic‐490T and Weber  reported in [35], in which several waterproofing materials, such as Sikalastic-490T and Weber Dry Dry  Lastic,  were  chosen  to  be  the  surface  coating  materials  for  PCM/lightweight  aggregates  Lastic, were chosen to be the effect  surface coating materials PCM/lightweight composites, composites,  and  the  good  on  overcoming  the  for PCM  leakage  problem aggregates was  experimentally  and the good effect onthe  overcoming themethod  PCM leakage problem was experimentally proven. Therefore, proven.  Therefore,  coating  film  has  the  application  potential  for  the  preparation  of  thePCM/granular porous material composites.  coating film method has the application potential for the preparation of PCM/granular porous material composites. Table 3. Leakage test results.  Table 3. Leakage test results.

Samples  Samples 1 



 

1 3  2 4  3 4 5  5 6  6 7  7 8  8

Proportion (wt %)  Diameter of Leakage  Diameter of Standard    Circle (mm)  Circle (mm)  Paraffin:EP  Proportion (wt %) Diameter of Leakage Diameter of Standard 35:65  31.50  Circle (mm) Circle (mm) Paraffin:EP 40:60  33.01  35:65 31.50 45:65  33.90  40:60 33.01 50:50  33.99  45:65 33.90 30.00  52.5:47.5  34.08  50:50 33.99 30.00 55:45  34.77  52.5:47.5 34.08 55:45 34.77 60:40  35.88  60:40 35.88 52.5:47.5 (coating film)  30.00 

52.5:47.5 (coating film)

30.00

η  η

105.00  110.03  105.00 113.00  110.03 113.30  113.00 113.60  113.30 115.90  113.60 115.90 119.60  119.60 100.00  100.00

 

(a) 

(b)

(c) 

(d)

  Figure  Comparison  leakage  performance for for  with  and  without coating coating film: film: (a,c) (a)  and  (c)  for  5 Figure 8. 8.  Comparison ofof  leakage performance with and without for Sample Sample 5 and (b) and (d) for Sample 8.  and (b,d) for Sample 8.

3.2. Thermal Property Analysis  3.2. Thermal Property Analysis Heat  conductivity  coefficient  of  PCMP  was  determined  to  be  0.057  W/(m∙K)  in  30  °C  and    Heat conductivity coefficient of PCMP was determined to be 0.057 W/(m¨ K) in 30 ˝ C and 0.054 W/(m∙K) in 10 °C. Figure 9 has shown the DSC test result of PCMP. Only one distinct peak in  0.054 K) inindicated  10 ˝ C. Figure 9 has shown the DSC test result of PCMP. Onlychange.  one distinct peak in the W/(m¨ DSC  curve  a  more  stable  performance  in  the  process  of  phase  The  phase 

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change point of PCMP was 21.6 °C, with a 4.2 °C difference compared to that of pure paraffin. The  fact  of Materials the  phase  and  2016, 9, 70change  point  shift  is  due  to  the  interaction  between  paraffin  molecules  10 of 16 micropore  interfaces  of  EP.  For  latent  heat,  it  was  found  to  be  56.3  J/g  for  PCMP,  through  calculating area integration at DSC peak curve. The latent‐heat ratio of PCMP to pure paraffin was  the DSC curve indicated a more stable performance in the process of phase change. The phase change ˝ C,paraffin  ˝ C difference 52.32%,  which  was was closed  percent  of  52.5%.  Additionally,  Table  has  point of PCMP 21.6 to  with a 4.2mass  compared to that of pure paraffin. The4 fact ofcompared  the phase change properties of PCMP to that of some composite PCMs with similar phase change point  phase change point shift is due to the interaction between paraffin molecules and micropore interfaces latent heat, itthat  was the  found to be 56.3 PCMP  J/g for PCMP, through calculating area integration at DSC and  range. ofIt EP. is For noteworthy  prepared  in  this  study  has  a  high  thermal  property  peak curve. The latent-heat ratio of PCMP to pure paraffin was 52.32%, which was closed to paraffin significant opportunity in building use.  mass percent of 52.5%. Additionally, Table 4 has compared phase change properties of PCMP to that of some PCMs with similar phase changeof  point range. It isthat  noteworthy the prepared Table  4.  composite Comparison  of  phase  change  property  PCMP  with  of  some that composite  PCMs    PCMP in this study has a high thermal property and significant opportunity in building use. in references.  Table 4. Comparison of phase change property of PCMP with that of some composite PCMs Phase Change Point  Latent Heat    in references. Composite PCM  References 

(°C)  Capric–lauric acid/gypsum  19.1  Phase Change Point Composite PCM (˝ C) Capric–palmitic acid/gypsum  22.9  Capric–lauric acid/gypsum 19.1 Capric–stearic acid/gypsum  23.8  Capric–palmitic acid/gypsum 22.9 Capric–palmitic acid/Vermiculite  Capric–stearic acid/gypsum 23.823.5  Capric–palmitic acid/Vermiculite 23.522.5  Methyl palmitate–stearate/wallboard  Methyl palmitate–stearate/wallboard 22.5 25# Paraffin/EP  25# Paraffin/EP 21.621.6 

(J/g)  35.2  References [11]  Latent Heat (J/g) 42.5  [25]  35.2 [11] 49  [26]  42.5 [25] 72.1  [27]  49 [26] 72.1 41.1  [27] [43]  41.1 [43] This research  56.3 56.3  This research

  Figure 9. DSC curves of PCMP. Figure 9.DSC curves of PCMP.   

3.3. Microstructure and Mechanical Property Analyses

3.3. Microstructure and Mechanical Property Analyses  In SEM picture of Figure 10, EP has obvious crack surface layer and three dimensional framework

In  SEM  picture  of  Figure  10,  EP These has  pores obvious  surface  layer  and  three  dimensional  structures within lots of micropores. usedcrack  to absorb paraffin are numerous with thin framework structures within lots of micropores. These pores used to absorb paraffin are numerous  wall, unfixed shapes, and size range of a few micrometers to several hundred micrometers. What is with  thin  unfixed  and  size  a  few  micrometers  hundred  more, wall,  due to the functionshapes,  of capillary action andrange  surfaceof  tension, the porous structureto  canseveral  contain and constraint the molecules of liquid paraffin. Thereby, this special structure provides adsorption effect micrometers. What is more, due to the function of capillary action and surface tension, the porous  for PCM. structure can contain and constraint the molecules of liquid paraffin. Thereby, this special structure  The SEM picture of PCMP is shown in Figure 11. It is obvious that the appearance of PCMP was provides adsorption effect for PCM.  different compared with that of EP. The paraffin with smooth surface and black color was contained The SEM picture of PCMP is shown in Figure 11. It is obvious that the appearance of PCMP  by the porous and laminated structure of EP (white color). It has been illustrated that EP with a was  different  compared  with  that structure of  EP. can The  paraffin  smooth  surface coating and  black  three-dimensional net micropore firmly absorbwith  paraffin. Additionally, film incolor  the was  contained by the porous and laminated structure of EP (white color). It has been illustrated that EP  outer surface can further encapsulate composite PCM particle. Thus, the microstructure of PCMP was with a three‐dimensional net micropore structure can firmly absorb paraffin. Additionally, coating  stable and tightness. film in the outer surface can further encapsulate composite PCM particle. Thus, the microstructure  of PCMP was stable and tightness.  In  the  mechanical  property  test  of  BESP  samples,  their  average  compressive  strength  was    4.61 N/mm2, which was about 2 N/mm2 higher than some EP insulation boards composed of plaster, 

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In the mechanical property test of BESP samples, their average compressive strength was 2 , which was about 2 N/mm2 higher than some EP insulation boards composed of plaster, 4.61 N/mm Materials 2016, 9, 70  11 of 16  Materials 2016, 9, 70  11 of 16  EP, and water [44]. Furthermore, the compressive strength of BESP was lower than that of some EP 2 concrete boards. After concrete maintenance, the compressive strength can reach to 7.53 N/mm2 for a concrete boards. After concrete maintenance, the compressive strength can reach to 7.53 N/mm concrete boards. After concrete maintenance, the compressive strength can reach to 7.53 N/mm2 for   for  kind of EP/PCM concrete boards, but the cement mortar accounted for 70% of total mass and, thus, a kind of EP/PCM concrete boards, but the cement mortar accounted for 70% of total mass and, thus,  a kind of EP/PCM concrete boards, but the cement mortar accounted for 70% of total mass and, thus,  the latent heat was decreased [14]. A deep study on the type and mass ratio for adhesives and their the latent heat was decreased [14]. A deep study on the type and mass ratio for adhesives and their  the latent heat was decreased [14]. A deep study on the type and mass ratio for adhesives and their  influence on the adhesive strength and thermal performance for BESP will be launched in the next influence on the adhesive strength and thermal performance for BESP will be launched in the next  influence on the adhesive strength and thermal performance for BESP will be launched in the next  work, so as to enhance the mechanical and thermal property of BESP. work, so as to enhance the mechanical and thermal property of BESP.  work, so as to enhance the mechanical and thermal property of BESP. 

(a)  (a) 

(b)  (b) 

Figure 10. SEM photographs of EP with different magnification: (a) 10 μm and (b) 20 μm.  Figure 10. SEM photographs of EP with different magnification: (a) 10 µm and (b) 20 µm. Figure 10. SEM photographs of EP with different magnification: (a) 10 μm and (b) 20 μm. 

(a)  (a) 

(b)  (b) 

Figure  11.  SEM  photographs  of  after  surface  film  with  magnification:    Figure 11. 11. SEM SEM  photographs  of  PCMP  PCMP  surface  film  coating  coating  with  different  different  magnification:  Figure photographs of PCMP after after  surface film coating with different magnification: (a) 10 µm   (a) 10 μm and (b) 20 μm.  (a) 10 μm and (b) 20 μm.  and (b) 20 µm.

3.4. Durability Analysis  3.4. Durability Analysis  3.4. Durability Analysis Figure  12  shows  the  DSC  curve  comparing  test  samples  before  and  after  a  Figure 12 12 shows shows the the  DSC  curve  comparing  samples  before  after  a  melting–freezing  melting–freezing  Figure DSC curve comparing testtest  samples before and and  after a melting–freezing cycle cycle  of  1000  times,  respectively.  For  the  whole  variation  tendency  of  thermal  properties  with  cycle  of  1000  times,  respectively.  For  the  whole  variation  tendency  of  thermal  properties  with  of 1000 times, respectively. For the whole variation tendency of thermal properties with increasing increasing temperature, the DSC curve before cycling is consistent with that after thermal cycling.  increasing temperature, the DSC curve before cycling is consistent with that after thermal cycling.  temperature, the DSC curve before cycling is consistent with that after thermal cycling. Then, as listed Then, as listed in Table 5, after 1000 cycles, the onset point, peak point, and end point of the DSC  Then, as listed in Table 5, after 1000 cycles, the onset point, peak point, and end point of the DSC  in Table 5, after 1000 cycles, the onset point, peak point, and end point of the DSC curve for PCMP have curve for PCMP have changed 0.5, 0.2, and −0.3 °C, respectively, followed by corresponding change  curve for PCMP have changed 0.5, 0.2, and −0.3 °C, respectively, followed by corresponding change  changed 0.5, 0.2, and ´0.3 ˝of  C,2.31%,  respectively, followed by corresponding ofchanges  the threecan  points rates  of  of  the  the  three  three  points  0.77%,  and  −1.08%,  −1.08%,  respectively. change These rates small  be  rates  points  of  2.31%,  0.77%,  and  respectively.  These  small  changes  can  be  of 2.31%, 0.77%, and ´1.08%, respectively. These small changes can be considered to not be significant considered to not be significant in magnitude for PCM applications [25]. Finally, the latent heat has  considered to not be significant in magnitude for PCM applications [25]. Finally, the latent heat has  in magnitude be  for PCMJ/g,  applications [25].J/g  Finally, the than  latent heatbefore  has decreased to be 55.8 J/g, which is decreased  decreased  to  to  be  55.8  55.8  J/g,  which  which  is  is  0.5  0.5  J/g  smaller  smaller  than  that  that  before  the  the  thermal  thermal  cycles.  cycles.  The  The  slight  slight  0.5 J/g smaller than that before the thermal cycles. The slight decrease was within a reasonable level decrease was within a reasonable level for a composite PCM [25].  decrease was within a reasonable level for a composite PCM [25].  for a In  composite PCMthe  [25]. In  conclusion,  conclusion,  the  reproducible  reproducible  thermal  thermal  performance  performance  for  for  the  the  test  test  sample  sample  has  has  indicated  indicated  that  that  PCMP  has  good  thermal  stability  and  reliability.  Additionally,  after  leakage  tests  for  PCMP  has  good  thermal  stability  and  reliability.  Additionally,  after  leakage  tests  for  the  the  sample  sample  with  with  thermal  thermal  cycles,  cycles,  it  it  was  was  confirmed  confirmed  that  that  PCMP  PCMP  still  still  has  has  no  no  leakage  leakage  during  during  long‐term  long‐term  use,  use,     as shown in Figure 13.  as shown in Figure 13. 

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In conclusion, the reproducible thermal performance for the test sample has indicated that PCMP has good thermal stability and reliability. Additionally, after leakage tests for the sample with thermal Materials 2016, 9, 70  12 of 16  cycles, it was confirmed that PCMP still has no leakage during long-term use, as shown in Figure 13. Materials 2016, 9, 70  12 of 16 

   Figure 12. DSC curve of PCMP before and after thermal cycling. Figure 12. DSC curve of PCMP before and after thermal cycling.  Figure 12. DSC curve of PCMP before and after thermal cycling.  Table 5. Phase change parameters before and after thermal cycles of PCMP. Table 5. Phase change parameters before and after thermal cycles of PCMP.  Table 5. Phase change parameters before and after thermal cycles of PCMP. 

Peak Point of  End Point of  Onset Point of    Latent Heat  Cycle  Cycle Onset Point  of Peak Point of End Point of Latent Heat Peak Point of  End Point of  Latent Heat  Cycle      Onset Point of  ˝ C)Phase Change ( ˝ C) Phase Change ( ˝°C) (J/g)  Number  ° C)  ° C)  C)  Phase Change ( Number Phase Change ( Phase Change ( Phase Change ( (J/g)  Number  Phase Change (°C)  Phase Change (°C)  Phase Change (°C)  (J/g) 0  0 21.6 21.6 26.0  27.8  56.3  26.0 27.8 56.3 0  21.6  26.0  27.8  56.3  1000 26.2 27.5 55.8 1000  22.1 22.1 26.2  27.5  55.8  1000  22.1  26.2  27.5  55.8 

  (a) 

(b) 

 

(a) PCMP  after  1000  thermal  cycles.  (a)  PCMP  (b)  Figure  13. Leakage Leakage test test  filter after paper  after  Figure 13. forfor  PCMP after 1000 thermal cycles. (a) PCMP was inwas  filterin  paper thermal thermal cycles; (b) PCMP was removed from filter paper after thermal cycles.  cycles;13.  (b)Leakage  PCMP was removed fromafter  filter 1000  paperthermal  after thermal cycles. Figure  test  for  PCMP  cycles.  (a)  PCMP  was  in  filter  paper  after  thermal cycles; (b) PCMP was removed from filter paper after thermal cycles. 

3.5. Dynamic Thermal Performance Analysis  3.5. Dynamic Thermal Performance Analysis 3.5. Dynamic Thermal Performance Analysis  In  this  test,  the  internal  temperatures  of  test  panels  were  measured  to  analyze  the  thermal  In this test, the internal temperatures of test panels were measured to analyze the thermal response response and, meanwhile, the heat flux between samples and the cold surface were also monitored  and, theinternal  heat fluxtemperatures  between samples andpanels  the cold surface were also to study In meanwhile, this  test,  the  of  test  were  measured  to monitored analyze  the  thermal  to study the thermal storage performance of panels. Furthermore, the hot surface temperature that  the thermal storage performance of panels. Furthermore, the hot surface temperature that varied response and, meanwhile, the heat flux between samples and the cold surface were also monitored  varied according to the 24‐h typical meteorological data in summer represented the outside temperature.  according to the 24-h typical meteorological data in summer represented the outside temperature. The to study the thermal storage performance of panels. Furthermore, the hot surface temperature that  The  dynamic  thermal  performances  for  BESP  and  EP  panels  (no  paraffin  in  the  EP  panel)  were  dynamic thermal performances for BESP and EP panels (no paraffin in the EP panel) were compared, varied according to the 24‐h typical meteorological data in summer represented the outside temperature.  compared, as shown in Figure 14, in which three important points can be highlighted as follows:  as dynamic  shown in Figure 14,performances  in which three for  important points can be highlighted as follows: The  thermal  BESP  and  EP  panels  (no  paraffin  in  the  EP  panel)  were 

compared, as shown in Figure 14, in which three important points can be highlighted as follows: 

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  Figure 14. Comparison of dynamic thermal performances for building energy storage panel (BESP)  Figure 14. Comparison of dynamic thermal performances for building energy storage panel (BESP) and expanded perlite (EP) panel over 24 h. and expanded perlite (EP) panel over 24 h. 

It was firstly obvious that with the external temperature changing, the temperature fluctuation  It was firstly obvious that with the external temperature changing, the temperature fluctuation of BESP was smaller than that of the EP panel, which can be illustrated by the fact that BESP was 3.08 ˝ C of BESP was smaller than that of the EP panel, which can be illustrated by the fact that BESP was  lower than the EP panel for the maximum temperatures. This was because the characteristic of PCM 3.08 °C lower than the EP panel for the maximum temperatures. This was because the characteristic  with awith  smalla temperature range in the melting/freezing process has reduced the large temperature of  PCM  small  temperature  range  in  the  melting/freezing  process  has  reduced  the  large  fluctuation. The smoother temperature variation for BESP has indicated that it can enhance the thermal temperature  fluctuation.  The  smoother  temperature  variation  for  BESP  has  indicated  that  it  can  comfort inside the building. enhance the thermal comfort inside the building.  The second observation is that a significant lagging effect of temperature response occurred in The second observation is that a significant lagging effect of temperature response occurred in  BESP. The peak temperature of internal BESP was 180 min later than that of the outside temperature, BESP.  peak  temperature  of  internal  BESP  was  was 180 only min 30later  that  temperature of  the  outside  butThe  the internal peak temperature lagging for EP panel min. than  The larger temperature, but  the  internal  peak  temperature  lagging for  EP  panel  was  only  30  min.  The larger  lagging has shown that BESP had a more prominent thermal inertia, and can decrease the energy temperature lagging has shown that BESP had a more prominent thermal inertia, and can decrease  consumption of buildings. the energy consumption of buildings.  Furthermore, the average heat flux across BESP was 17.11 W/m2 smaller than that across EP 2 . The lower panel, followed by decrease 57.76was  W/m heat fluxthan  of BESP implied Furthermore,  the maximum average  heat heat flux flux  across of BESP  17.11  W/m2  smaller  that  across  EP  2 less heat was transmitted through the panel, compared with that. The lower heat flux of BESP implied  of EP panel. This was due to, in the panel, followed by maximum heat flux decrease of 57.76 W/m heat transmission process, BESP can store more heat through PCM melting with heat absorption. less  heat  was  transmitted  through  the  panel,  compared  with  that  of  EP  panel.  This  was  due  to,    in the heat transmission process, BESP can store more heat through PCM melting with heat absorption.  4. Conclusions In this study, a novel composite PCM particle (PCMP) with a coating film has been prepared, 4. Conclusions 

through paraffin incorporated with EP by vacuum adsorption. With the coating film process completed In this study, a novel composite PCM particle (PCMP) with a coating film has been prepared,  for PCM particles, the leakage problem in composite PCM has been effectively resolved. Then, through paraffin incorporated with EP by vacuum adsorption. With the coating film process completed  a thermal storage panel–BESP was fabricated with PCMPs by a mold pressing method with a certain amount of adhesives. Furthermore, the related propertiesPCM  of PCMP dynamic thermal performance for  PCM  particles,  the  leakage  problem  in  composite  has and been  effectively  resolved.  Then,  a  of BESP have been studied and analyzed, and several conclusions were obtained, as following: thermal storage panel–BESP–was fabricated with PCMPs by a mold pressing method with a certain 

amount of adhesives. Furthermore, the related properties of PCMP and dynamic thermal performance  ‚ The best proportions of paraffin and EP in PCMP were ascertained to be 52.5 wt % and 47.5 wt %, of BESP have been studied and analyzed, and several conclusions were obtained, as following:  respectively, and no liquid paraffin oozed from PCMP in leakage tests, after applying a coating 

onproportions  PCMP. The film best  of  paraffin  and  EP  in  PCMP  were  ascertained  to  be  52.5  wt  %  and    The phase change temperature and latent heat of PCMP were measured to be 21.6 ˝ C and 56.3 J/g, 47.5  wt  %,  respectively,  and  no  liquid  paraffin  oozed  from  PCMP  in  leakage  tests,  after  respectively, through DSC. applying a coating film on PCMP.  ‚ There was no significant degradation of thermal properties for PCMP sample after repeating The  phase  change  temperature  and  latent  heat  of  PCMP  were  measured  to  be  21.6  °C  and    melting and freezing cycles 1000 times. 56.3 J/g, respectively, through DSC.  There  was  no  significant  degradation  of  thermal  properties  for  PCMP  sample  after  repeating  melting and freezing cycles 1000 times.  A high‐quality thermal performance, including small temperature fluctuation, large temperature  lagging, and high thermal storage capacity for BESP, was confirmed in a dynamic temperature  ‚

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A high-quality thermal performance, including small temperature fluctuation, large temperature lagging, and high thermal storage capacity for BESP, was confirmed in a dynamic temperature input test.

BESP, a method of application for PCMP, was developed and its good thermal performance was obtained, however, related other characteristics, such as water-resistance ability and adhesive affection, etc., have not been involved in this study. There is, therefore, the need to complete the BESP property research in future work, in order to achieve the BESP large-scale application in buildings. Acknowledgments: This work was supported by National Natural Science Foundation of China (Project No. 51408184), Tianjin Natural Science Foundation (Project No. 15JCQNJC07800), Outstanding Youth Fund Projects in Hebei Province Department of Education (Project No. YQ2014005) and Tianjin Urban & Rural Construction Commission Funded Project (Project No. 2015-13). Author Contributions: Xiangfei Kong and Xian Rong conceived and designed the experiments; Yuliang Zhong performed the experiments; Chunhua Min analyzed the data; Chengying Qi contributed materials; Xiangfei Kong wrote the paper. Conflicts of Interest: The authors declare no conflict of interest.

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Expanded Perlite: Preparation and Thermal Performance Study.

This study is focused on the preparation and performance of a building energy storage panel (BESP). The BESP was fabricated through a mold pressing me...
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