Analytical solutions of heat storage and heat transfer performance of parallel‐plate regenerators in Stirling cycle

2020 ◽  
Author(s):  
Huanguang Wang ◽  
Yunhao Bao ◽  
Yuming Tang ◽  
Meng Liu ◽  
Bilin Zhang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Analytical Solutions ◽  
Parallel Plate ◽  
Heat Transfer Performance ◽  
Heat Storage ◽  
Transfer Performance ◽  
Stirling Cycle

Performance of a Compact Cooling Unit Utilizing Air-Water Mist Flow

1983 ◽  
Vol 105 (1) ◽  
pp. 18-24 ◽  
Author(s):  
T. Aihara ◽  
R. Saga
Keyword(s):  
Heat Transfer ◽  
Parallel Plate ◽  
Heat Transfer Performance ◽  
Thermal Conditions ◽  
Water Mist ◽  
Transfer Performance ◽  
Cooling Unit ◽  
Wide Range ◽  
Mist Flow ◽  
Plate Channel

Performance of a new compact cooling unit for semiconductors, being composed of an atomizer, a fan, and a heat-dissipating surface with no fin, has been measured over a wide range of the mass flow rate of spray water, m˙, and the wall heat flux. The heat transfer performance of the present compact, unit with m˙ = 0 to 1.05 g/s, attains 1.8 to 20 times that of the parallel-plate channel under the same thermal conditions.

Experimental Study on the Stability and Thermophysical Properties of Binary Propanol-Water Mixtures Based Phase Change Microencapsule Suspensions

2013 ◽  
Author(s):  
Liang Wang ◽  
Li Liu ◽  
Yifei Wang ◽  
Lei Chai ◽  
Zheng Yang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Thermophysical Properties ◽  
Heat Transfer Performance ◽  
Heat Storage ◽  
Experimental Result ◽  
Thermal Constant ◽  
Transfer Performance ◽  
Thermal Fluids ◽  
Alcohol Water

Phase change microencapsules are the microsized particles made of phase change materials (paraffin wax ect.) sealed by the thin shell (polymer ect.) via the methods of microencapsulation. During last decade, due to the large amount of melting/solidifying heat, much attention have been paid on their application in environmental control, building, textiles and electronics ect. Also the novel thermal fluids by phase change microencapsules suspending in the traditional thermal fluids have shown their superior heat storage density and convective heat transfer performance, which can behave as heat storage media and heat transfer media simultaneously. However, the density difference between the phase change microencapsules and tranditional unitary fluid would lead to the unstable suspending states which seriously affect the heat storage and heat transfer performance. Binary mixtures such as alcohol-water etc have already played the important roles in the heat transfer equipments. In this paper, binary propanol-water mixtures of various proportion were formulated as the base fluids, and their stabilities were studied. The result shows that binary propanol-water mixtures with the desity of 941kg/m3 showed the best stability and no stratification was found after standing for 48 hours. The morphology and diameter distribution of the microencapsule particles were tested by the scanning electron microscope (SEM) and Malvern Nanosizer respectively, and the result show that the diameter of the particles is in the range of 10–80μm with the average value of 26.4μm. The phase change enthalpy and the effective heat capacity of phase change microencapsule suspensions with the concentration of 10–40wt% were measured by the differencial scanning calorimeter (DSC) and it was found the phase change enthalpy of the phase change microencapsule is 152.8J/g and the undercooling is only 7.3°C. The effect of concentration and temperature on the rheological behavior and viscosities of suspensions were experimentally studied by the TA DHR-G2 rheometer. The result shows that the suspensions behave as Newtonian fluids even when the concentration is as high as 40wt% and the viscosities fit well with Vand model. By the Hot Disk 2500S thermal constant analyzer (Sweden), the thermal conductivities of 0–40wt% suspensions were tested at 20–70°C and the variation was analyzed further. The concentration and expansion of MPCM particles during the phase change period were found to affect the thermal expansion coefficient of the MPCM suspensions obviously. The above experimental result and analyzation of stability and thermophysical properties will provide a complete and important data for the application in heat storage and heat transfer.

Heat Transfer Enhancement in Ferrofluids Flow in Micro and Macro Parallel Plate Channels: A Comparative Numerical Study

2017 ◽  
Vol 10 (2) ◽  
Author(s):  
Aditi Sengupta ◽  
P. S. Ghoshdastidar
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Enhancement Factor ◽  
Parallel Plate ◽  
Heat Transfer Performance ◽  
Numerical Study ◽  
Transfer Performance ◽  
Nanoparticle Concentration ◽  
Transfer Enhancement ◽  
Fully Developed Flow

This paper presents a comparative numerical study of heat transfer enhancement in steady, laminar, hydrodynamically fully developed flow of water-based ferrofluids under no magnetic field in micro and macro parallel plate channels subjected to constant equal heat fluxes on its top and bottom, considering Brownian diffusion and thermophoresis of ferroparticles in the base fluid. While the microchannel results match very well with the experimental data for water in an equivalent microtube (Kurtoglu et al., 2014, “Experimental Study on Convective Heat Transfer Performance of Iron Oxide Based Ferrofluids in Microtubes,” ASME J. Therm. Sci. Eng. Appl., 6(3), p. 034501.), the numerically predicted enhancement factor in ferrofluids is much below that for the same microtube. A detailed parametric study points to possible inaccuracies in the experimental results of Kurtoglu et al. (2014, “Experimental Study on Convective Heat Transfer Performance of Iron Oxide Based Ferrofluids in Microtubes,” ASME J. Therm. Sci. Eng. Appl., 6(3), p. 034501.) for ferrofluids. The nanoparticle concentration profiles in the microchannel flow reveal that (a) the nanoparticle concentration at the wall increases with axial distance, (b) the wall nanoparticle concentration decreases with increasing heat flux, and (c) the concentration profile of nanoparticles is parabolic at the exit. A comparison of thermally developing flow in microchannel and macrochannel of the same length (0.025 m) indicates that the enhancement factor at the microchannel exit is 1.089 which is only marginally higher than that at the macrochannel exit in the heat flux range of 20–80 kW/m2. On the other hand, for the thermally fully developed flow in both microchannel and macrochannel of the same length (0.54 m) the maximum enhancement factor for the macrochannel is 1.7, as compared to 1.1 for the microchannel, in the heat flux range of 1–4 kW/m2.

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