An Experimentally Validated Evaporative Phase Change Heat Transfer Model for Low Mass Flux Applications using R134a in Plate Heat Exchangers

Abstract As thermal protection substrates for wearable electronics, functional soft composites made of polymer materials embedded with phase change materials and metal layers demonstrate unique capabilities for the thermal protection of human skin. Here, we develop an analytical transient phase change heat transfer model to investigate the thermal performance of a wearable electronic device with a thermal protection substrate. The model is validated by experiments and the finite element analysis (FEA). The effects of the substrate structure size and heat source power input on the temperature management efficiency are investigated systematically and comprehensively. The results show that the objective of thermal management for wearable electronics is achieved by the following thermal protection mechanism. The metal thin film helps to dissipate heat along the in-plane direction by reconfiguring the direction of heat flow, while the phase change material assimilates excessive heat. These results will not only promote the fundamental understanding of the thermal properties of wearable electronics incorporating thermal protection substrates, but also facilitate the rational design of thermal protection substrates for wearable electronics.

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Performance of Plate Heat Exchangers Used as Refrigerant Liquid-Overfeed Evaporators

2010 14th International Heat Transfer Conference, Volume 4 ◽

10.1115/ihtc14-22095 ◽

2010 ◽

Cited By ~ 1

Author(s):

Jianchang Huang ◽

Thomas J. Sheer ◽

Michael Bailey-McEwan

Keyword(s):

Heat Transfer ◽

Heat Flux ◽

Pressure Drop ◽

Mass Flux ◽

Heat Exchangers ◽

Strong Dependence ◽

Nucleate Boiling ◽

Small Range ◽

Plate Heat ◽

System Pressure

The heat transfer and pressure drop characteristics of plate heat exchangers were measured, when used as refrigerant liquid over-feed evaporators. The three units all had 24 plates but with different chevron-angle combinations of 28°/28°, 28°/60°, and 60°/60°. R134a flowing upwards was used as the refrigerant, in a counter-current arrangement with water flowing on the other side. Heat transfer and pressure drop measurements were made over a range of mass flux, heat flux and corresponding outlet vapour fractions. The effect of system pressure on the evaporator performance was not evaluated due to the small range of evaporating temperature. Experimental data were reduced to obtain the refrigerant-side heat transfer coefficient and frictional pressure drop. The results for heat transfer showed a strong dependence on heat flux and weak dependence on mass flux and vapour fraction. Furthermore, the chevron angle had a small influence on heat transfer but a large influence on frictional pressure drops. Along with observations that were obtained previously on large ammonia and R12 plate evaporators, it is concluded that the dominating heat transfer mechanism in this type of evaporator is nucleate-boiling rather than forced convection. For the two-phase friction factor, various established methods were evaluated; the homogeneous treatment gives good agreement.

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Parallel Heat Transfer Model of a Panel with Phase Change Material for Thermal Storage Applications Computed on Graphics Processing Units

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1077.118 ◽

2014 ◽

Vol 1077 ◽

pp. 118-123 ◽

Cited By ~ 1

Author(s):

Lubomír Klimeš ◽

Pavel Charvát ◽

Milan Ostrý ◽

Josef Stetina

Keyword(s):

Heat Transfer ◽

Phase Change ◽

Phase Change Material ◽

Graphics Processing Units ◽

Parallel Implementation ◽

Heat Transfer Model ◽

Transfer Model ◽

Wide Range ◽

Graphics Processing ◽

Change Material

Phase change materials have a wide range of application including thermal energy storage in building structures, solar air collectors, heat storage units and exchangers. Such applications often utilize a commercially produced phase change material enclosed in a thin panel (container) made of aluminum. A parallel 1D heat transfer model of a container with phase change material was developed by means of the control volume and effective heat capacity methods. The parallel implementation in the CUDA computing architecture allows the model for running on graphics processing units which makes the model very fast in comparison to traditional models computed on a single CPU. The paper presents the model implementation and results of computational model benchmarking carried out with the use of high-level and low-level GPUs NVIDIA.

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Transient Temperature Response of Variable Flow Heat Exchangers in a Marnoch Heat Engine

Journal of Heat Transfer ◽

10.1115/1.4028176 ◽

2014 ◽

Vol 136 (11) ◽

Author(s):

P. Saneipoor ◽

G. F. Naterer ◽

I. Dincer

Keyword(s):

Heat Transfer ◽

Heat Exchangers ◽

Heat Engine ◽

Heat Transfer Model ◽

Transient Temperature ◽

Transfer Model ◽

Gas Temperature ◽

Variable Flow ◽

Flow Heat ◽

Shell And Tube

Within a Marnoch heat engine (MHE), a water/glycol mixture transfers heat from the heat source into a set of variable flow heat exchangers and removes heat from adjoining cold heat exchangers. The compressed dry air is used as the working medium in this heat engine. The MHE has four shell and tube heat exchangers, which operate transient and variable flow conditions. A new transient heat transfer model is developed to predict this transient behavior of the heat exchangers for different flow regimes and temperatures. The results from the model are validated against experimental results from an MHE prototype. The heat transfer model shows 85% agreement with measured data from the MHE prototype for the individual heat exchangers. This model can be used for similar shell and tube heat exchangers with straight or U-shaped tubes. The heat transfer model predicts the gas temperature on the shell side, when a step change is imposed on the liquid entering the tubes.

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A conjugate heat transfer model for unconstrained melting of macroencapsulated phase change materials subjected to external convection

International Journal of Heat and Mass Transfer ◽

10.1016/j.ijheatmasstransfer.2019.119205 ◽

2020 ◽

Vol 149 ◽

pp. 119205 ◽

Cited By ~ 2

Author(s):

Daniel Hummel ◽

Stefan Beer ◽

Andreas Hornung

Keyword(s):

Heat Transfer ◽

Phase Change ◽

Conjugate Heat Transfer ◽

Phase Change Materials ◽

Heat Transfer Model ◽

Transfer Model

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Phase-Change Heat Transfer in Microsystems

Journal of Heat Transfer ◽

10.1115/1.2410008 ◽

2006 ◽

Vol 129 (2) ◽

pp. 101-108 ◽

Cited By ~ 44

Author(s):

Ping Cheng ◽

Hui-Ying Wu ◽

Fang-Jun Hong

Keyword(s):

Heat Transfer ◽

Phase Change ◽

Mass Flux ◽

Annular Flow ◽

Pulse Heating ◽

Flow Boiling ◽

Mist Flow ◽

Flow Condensation ◽

Phase Change Heat Transfer ◽

Condensation Flow

Recent work on miscroscale phase-change heat transfer, including flow boiling and flow condensation in microchannnels (with applications to microchannel heat sinks and microheat exchangers) as well as bubble growth and collapse on microheaters under pulse heating (with applications to micropumps and thermal inkjet printerheads), is reviewed. It has been found that isolated bubbles, confined elongated bubbles, annular flow, and mist flow can exist in microchannels during flow boiling. Stable and unstable flow boiling modes may occur in microchannels, depending on the heat to mass flux ratio and inlet subcooling of the liquid. Heat transfer and pressure drop data in flow boiling in microchannels are shown to deviate greatly from correlations for flow boiling in macrochannels. For flow condensation in microchannels, mist flow, annular flow, injection flow, plug-slug flow, and bubbly flows can exist in the microchannels, depending on mass flux and quality. Effects of the dimensionless condensation heat flux and the Reynolds number of saturated steam on transition from annular two-phase flow to slug/plug flow during condensation in microchannels are discussed. Heat transfer and pressured drop data in condensation flow in microchannels, at low mass flux are shown to be higher and lower than those predicted by correlations for condensation flow in macrochannels, respectively. Effects of pulse heating width and heater size on microbubble growth and collapse and its nucleation temperature on a microheater under pulse heating are summarized.

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