Second law analysis and optimization of solar hot water systems

(1989) Second law analysis and optimization of solar hot water systems. Masters thesis, King Fahd University of Petroleum and Minerals.


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Traditionally solar systems are analyzed on the basis of first law of thermodynamics which dictates that energy in a system is not lost, but it is trnsferred from one form to another. However, first law doesn't account for irreversibilities (entropy generation) accompanied during heat transfer across finite temperature difference, fluid friction, mixing of fluids etc. In this investigation solar domestic hot water (SDHW) systems were analyzed from the standpoint of second law of thermodynamics. Attention was mainly focussed on analysis and optimization of solar hot water systems for minimum entropy generation while satisfying dynamic, thermal, and total hot water requirement constraints. The SDHW systems were simulated using actual weather data while providing the necessary hot water requirement in accordance with Rand, Vitro and ASHRAE hourly load profiles. Systems were simulated for various tank volume to collector area and total load mass flow over rank volume ratios. In each case entropy generated and auxiliary energy consumed were obtained. For every case simulated, the distribution of load mass flow during 24 hour period was obtained by minimizing total entropy generation during the same period. For each case, the total entropy generated and auxiliary energy consumed were compared with the corresponding simulation results. Optimization of SDHW systems for minimum entropy generation show considerable reduction in entropy generation and auxiliary energy consumption. Optimization studies point out that for a particular system, entropy generation per liter of hot water withdrawal is not a strong function of flow profile. Both simulation and optimization results indicate that for minimum entropy generation and minimum auxiliary energy consumption load should be approximately equal to storage tank size for one day's data and tank size to collector area ratio should be approximately between 50 to 70.

Item Type: Thesis (Masters)
Subjects: Mechanical
Department: College of Engineering and Physics > Mechanical Engineering
Committee Advisor: Kar, Abdul Kerim
Committee Members: Said, A. S. and Al-Sulaiman, Faleh A.
Depositing User: Mr. Admin Admin
Date Deposited: 22 Jun 2008 14:02
Last Modified: 01 Nov 2019 14:00