scholarly journals Modeling PCM Phase Change Temperature and Hysteresis in Ventilation Cooling and Heating Applications

Energies ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 6455
Author(s):  
Yue Hu ◽  
Rui Guo ◽  
Per Kvols Heiselberg ◽  
Hicham Johra
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Phase Change ◽  
Building Energy ◽  
Heat Transfer Process ◽  
Strong Impact ◽  
Phase Change Temperature ◽  
Change Temperature ◽  
Modelling Methods

Applying phase change material (PCM) for latent heat storage in sustainable building systems has gained increasing attention. However, the nonlinear thermal properties of the material and the hysteresis between the two-phase change processes make the modelling of PCM challenging. Moreover, the influences of the PCM phase transition and hysteresis on the building thermal and energy performance have not been fully understood. This paper reviews the most commonly used modelling methods for PCM from the literature and discusses their advantages and disadvantages. A case study is carried out to examine the accuracy of those models in building simulation tools, including four methods to model the melting and freezing process of a PCM heat exchanger. These results are compared to experimental data of the heat transfer process in a PCM heat exchanger. That showed that the four modelling methods are all accurate for representing the thermal behavior of the PCM heat exchanger. The model with the DSC Cp method with hysteresis performs the best at predicting the heat transfer process in PCM in this case. The impacts of PCM phase change temperature and hysteresis on the building energy-saving potential and thermal comfort are analyzed in another case study, based on one modelling method from the first case study. The building in question is a three-room apartment with PCM-enhanced ventilated windows in Denmark. The study showed that the PCM hysteresis has a larger influence on the building energy consumption than the phase change temperature for both summer night cooling applications and for winter energy storage. However, it does not have a strong impact on the yearly total energy usage. For both summer and winter transition seasons, the PCM hysteresis has a larger influence on the predicted percentage of dissatisfied (PPD) than the phase change temperature, but not a strong impact on the transition season average PPD. It is therefore advised to choose the PCM hysteresis according to whether it is for a summer night cooling or a winter solar energy storage application, as this has a significant impact on the system’s overall efficiency.

Numerical Simulation on Phase-Change Heat Transfer Within Microencapsulated Phase Change Material

2003 ◽  
Author(s):  
Yu Rao ◽  
Guiping Lin
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Control Volume ◽  
Computation Model ◽  
Carrier Fluid ◽  
Phase Change Temperature ◽  
Microencapsulated Phase Change Material ◽  
Change Temperature ◽  
Phase Change Heat Transfer ◽  
Change Material

A source item-based computation model is developed for analysing phase-change heat transfer within Microencapsulated PCM suspending in a flowing carrier fluid to enhance convective heat transfer, with the consideration of phase-change temperature range and varying thermal properties. Solution is obtained by developing a control volume-based finite difference code, in which TDMA method combined with under-relaxation is used to solve a strong nonlinear equation. The code developed for this study can be used for evaluating Microencapsulated PCM suspension and instructing the preparation of Microencapsulated PCM.

Heat Transfer Characteristics of Microencapsulated Phase Change Material Slurry Flows Under a Constant Heat Flux Boundary

2011 ◽  
Author(s):  
James A. Howard ◽  
Patrick A. Walsh
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Phase Change ◽  
Phase Change Material ◽  
Heat Transfer Characteristics ◽  
Phase Change Temperature ◽  
Transfer Characteristics ◽  
Microencapsulated Phase Change Material ◽  
Change Temperature ◽  
Change Material

This paper investigates laminar heat transfer characteristic of two-phase microencapsulated phase change material (MPCM) suspension flows within mini-channels under a constant wall heat flux boundary. Capsules containing paraffin wax with phase change temperature between 35.1°C and 44°C are examined and found to be well suited for electronics cooling applications using liquid cold plate technologies. In particular, it is shown that the large thermal capacity of MPCM slurries around the phase change temperature can lead towards greater isothermality of isoflux systems, a characteristic of significant interest to telecommunication, laser and biomedical applications. The principal focus of the study is to examine heat transfer characteristics within standard tube flow geometries, quantify the heat transfer augmentation/degradation observed and finally, elucidate the mechanisms from which these result. Through the study volume concentrations of the MPCM slurry were varied between 30.2% and 5.03%. High resolution local heat transfer measurements were obtained using infrared thermography and results presented in terms of local Nusselt number versus inverse Graetz parameter. These spanned both the thermal entrance and the fully developed flow regions with inverse Graetz number ranging from 10−3 to 100. Results show that significant heat transfer enhancements are attainable via the use of MPCM slurries over conventional single phase coolants. Overall, the study highlights mechanisms that lead to significant heat transfer enhancements in heat exchange devices employing micro-encapsulated phase change material slurries.

scholarly journals Utilization of an Air-PCM Heat Exchanger in Passive Cooling of Buildings: A Simulation Study on the Energy Saving Potential in Different European Climates

Energies ◽  
2019 ◽  
Vol 12 (6) ◽  
pp. 1133 ◽  
Author(s):  
Pavel Charvát ◽  
Lubomír Klimeš ◽  
Martin Zálešák
Keyword(s):  
Heat Exchanger ◽  
Phase Change ◽  
Energy Saving ◽  
Operating Conditions ◽  
Heat Of Fusion ◽  
Passive Cooling ◽  
Phase Change Temperature ◽  
Set Point ◽  
Energy Saving Potential ◽  
Change Temperature

The energy saving potential (ESP) of passive cooling of buildings with the use of an air-PCMheat exchanger (cold storage unit) was investigated through numerical simulations. One of the goals of the study was to identify the phase change temperature of a PCM that would provide the highest energy saving potential under the specific climate and operating conditions. The considered air-PCM heat exchanger contained 100 aluminum panels filled with a PCM. The PCM had a thermal storage capacity of 200 kJ/kg in the phase change temperature range of 4 ∘ C. The air-PCM heat exchanger was used to cool down the outdoor air supplied to a building during the day, and the heat accumulated in the PCM was rejected to the outdoors at night. The simulations were conducted for 16 locations in Europe with the investigated time period from 1 May–30 September. The outdoor temperature set point of 20 ∘ C was used for the utilization of stored cold. In the case of the location with the highest ESP, the scenarios with the temperature set point and without the set point (which provides maximum theoretical ESP) were compared under various air flow rates. The average utilization rate of the heat of fusion did not exceed 50% in any of the investigated scenarios.

Heat Transfer During Heating and Cooling of a Packed Bed Comprised of Encapsulated Phase Change Material

2017 ◽  
Author(s):  
Glen O. West ◽  
Kent S. Udell
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Internal Heat ◽  
Packed Bed ◽  
High Energy ◽  
Air Injection ◽  
Cold Air ◽  
Phase Change Temperature ◽  
Hot Air ◽  
Change Temperature

Phase change materials (PCMs) are attractive components of thermal energy storage systems due to their high energy densities and the relatively small temperature differences needed for effective charging and discharging. In this study, experimental data were examined in order to better understand energy exchange in packed beds and porous media comprised of solid/liquid phase change capsules. Air was used as the heat transfer fluid; hot air was injected in order to drive the melting process, while cold air was injected to accomplish freezing or solidification of the PCM. Theory was developed to describe the temperature variations throughout the bed. Temperatures in the bed were found to vary exponentially near the phase change fronts. For cold air injection into a bed initially above the phase change temperature, a second wave was observed ahead of the phase change front that can be described as a broadening traveling thermal wave due to diffusion/dispersion. For hot air injection into a packed bed of solidified PCM capsules initially at a temperature below the phase change temperature, the thermal waves in the cold region showed isotherm velocity retardation due to incomplete thawing. A shrinking core model of the melting or solidification of the PCM in the capsules was developed to document the internal heat transfer constraints within the capsules. The results of that study support the conclusion that slower wave velocities occur due to partial melting.

scholarly journals Transient Analysis of Heat Transfer Across the Residential Building Roof with Pcm and Wood Wool- A Case Study by Numerical Simulation Approach

2013 ◽  
Vol 59 (4) ◽  
pp. 483-497 ◽  
Author(s):  
D. Prakash ◽  
P. Ravikumar
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Phase Change ◽  
Phase Change Material ◽  
Transient Analysis ◽  
Residential Building ◽  
Building Roof ◽  
Type 3 ◽  
Change Material

Abstract In this paper, transient analysis on heat transfer across the residential building roof having various materials like wood wool, phase change material and weathering tile is performed by numerical simulation technique. 2-dimensional roof model is created, checked for grid independency and validated with the experimental results. Three different roof structures are included in this study namely roof with (i). Concrete and weathering tile, (ii). Concrete, phase change material and weathering tile and (iii). Concrete, phase change material, wood wool and weathering tile. Roof type 3 restricts 13% of heat entering the room in comparison with roof having only concrete and weathering tile. Also the effect of various roof layers’ thickness in the roof type 3 is investigated and identified that the wood wool plays the major role in arresting the entry of heat in to the room. The average reduction of heat is about 10 % for an increase of a unit thickness of wood wool layer.

Investigation of Heat Transfer for Shell-Tube Fuel-Cooled Heat Exchanger

2013 ◽  
Vol 378 ◽  
pp. 459-465
Author(s):  
Ya Guo Lu ◽  
Peng Fei Zhu
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Relative Error ◽  
Absolute Error ◽  
Heat Transfer Characteristics ◽  
Shell Side ◽  
Transfer Characteristics ◽  
Aero Engine ◽  
The Absolute

A calculate method based on ε-NTU model for heat transfer characteristics of shell-tube fuel-cooled heat exchanger of aero-engine lubrication system was built. The heat convection coefficient was obtained by a dimensionless curve (Re~StPr2/3), which was detailed introduced as well. A case study was executed at last. The absolute error of the outlet lubrication of the tube side and the shell side between the value of calculation and experiment was less than ±10°C, and the relative error was less than 6.5%. The absolute error of the heat transferred between calculation and experiment was less than ±0.9kW, and the relative error was less than 7.4%. It indicates that the mothod is available for the investigation of heat transfer characteristics of shell-tube fuel-cooled heat exchanger.

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