Analysis of two-phase flow in a double-pipe heat exchanger filled with porous media

Apr 12, 2020

Journal International Journal of Heat and Mass Transfer

publisher http://www.sciencedirect.com/science/journal/24519049

DOI https://doi.org/10.1016/j.ijheatmasstransfer.2020.119799

Volume 156

In this article, two-phase flow in a double-pipe porous heat exchanger and associated phase change processes has been numerically analysed to investigate the impacts of the relative permeabilities. The modified h-formulation along with the assumption of Local Thermal Equilibrium condition has been employed. Finite Volume Method (FVM) has been used to discretise the governing equations. The solutions of incomplete evaporation process have been validated with the experiments and they show an excellent agreement between them. The pertinent parameters have been systematically investigated to demonstrate the importance of the above mentioned influences on the complete evaporation process. It has been observed that the power index of the relative permeabilities for either liquid or vapour region has a significant effects on the beginning and ending of phase change operation, especially when the steam is formed inside the pipe. Comparison between results obtained with maximum and minimum values of the power index indicated that the latter value must be used while simulating the complete evaporation process, particularly for very low inlet Reynolds number and very high wall temperature. It is also evident that the operating conditions and geometric parameters of the heat exchanger have been substantially changed the location of the beginning and ending of the phase change process. On the other hand, the properties of porous media have only minor influence.

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Experimental Investigation to Retrofit HCFC-22 Window Air Conditioner with R-407C

Sep 1, 2019

Journal 2019 International Conference on Advanced Science and Engineering (ICOASE)

publisher IEEE

DOI https://doi.org/10.1016/j.tsep.2019.100359

In this paper, refrigerant R407c has been experimentally investigated to retrofit the refrigerant R22 in the existing systems. Window type air conditioner with capacity of 7.0 kW using R22 as working fluid has been selected to conduct the experimental work. The two refrigerants R22 and R407C have same operation conditions are selected in order to compare these thermal performances. The results showed that the refrigeration effect of R22 is higher than those for R407C. Consequently, the coefficient of performance COP of R407C is lower than R22. Also, the discharge temperature of the R407C is lower than those of R22. The pressure drop in the evaporator and condenser of the R407C less than those for R22. Moreover, the condensation temperature decreases along the length of the condenser coil for two refrigerants. The condensation temperatures for R22 is higher than the condensation temperatures of R407C at same ambient temperature. Finally, R407C can be considered as a suitable replacement for R22 with a slight variation in the performance with no need to change any part of the refrigeration system.

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Experimental Investigation on the Influence of Duct Material on the Heat Gain to Air Flow

Apr 1, 2019

Journal Fifth International Engineering Conference on Developments in Civil & Computer Engineering Applications 2019 - (IEC2019) - Erbil - IRAQ

publisher IEEE

DOI https://doi.org/10.1016/j.tsep.2019.100359

In this study, the influence of the duct material and insulation on the air heat gain is experimentally investigated. The objective of this study is to present the results of experimental evaluating of the heat gained by the air that flows through a square duct using several materials and insulations. The materials were galvanized steel duct without insulation, galvanized steel duct with 25 mm glass wool insulation and foam duct with a density of 50 kg/m³. Also, for each case, the air flow rate was varied to determine the amount of heat gain. The tabulate data has been drawn by sigma plot software version 10. The results showed that the rate of heat gain in a foam air duct is lower than galvanized iron with insulation and without insulation approximately by 56% and 69%, respectively. In addition, the heat transfer coefficient has a direct proportion with the air flow rate.

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Performance analysis of hybrid photovoltaic thermal solar system in Iraq climate condition

Feb 1, 2019

Journal Thermal Science and Engineering Progress

publisher http://www.sciencedirect.com/science/journal/24519049

DOI https://doi.org/10.1016/j.tsep.2019.100359

In this paper, the hybrid photovoltaic/thermal solar domestic hot water (PVT-SDHW) has been numerically investigated to determine its thermal and electrical performance of a house consists of 5 persons in Iraq climate environment. Detailed mathematical formulation of the PVT-SDHW system have been developed. To validate the feasibility of the developed numerical code, the present results have been compared with the experimental and numerical results and the comparison shows a good agreement between them. The PVT-SDHW system has been tested using the solar radiation data of Mosul city/Iraq that was estimated from ASHRAE Clear Sky Model. The auxiliary heater power, electrical power generation, storage tank water temperature, thermal solar fraction and demand electrical fraction have been analysed. The packing factor (rc) has been considered in this study as a key parameter. The results show that the minimum auxiliary heater power required and the maximum thermal solar fraction occurred when rc = 0. Most importantly, the results also indicated that the electricity production has been increased by increment in rc. For rc = 1, it has been found that the PVT-SDHW provides hot water between 61.7% and 83% and electricity generation between 24.5% and 43.9% needed by a family of five persons for various months.

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