Design of thermodynamic charts for hydrocarbon mixtures and influence of operating temperatures for solar absorption cooling cycle

Journal Article · Wed Oct 01 04:00:00 EDT 1997 · Energy Sources

DOI:https://doi.org/10.1080/00908319708908899· OSTI ID:562182

Eissa, M A.W. ^[1]

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1. Egyptian National Research Centre, Cairo (Egypt). Solar Energy Dept.

A complete study is developed for hydrocarbon mixtures to determine their suitability as working fluids for solar absorption cooling systems. The results show that the most suitable one is composed of 50% by mole n-butane and 50% by mole h-heptane. This mixture can be used at generation temperatures t{sub g} between 55 C and 65 C with a maximum working pressure of 2.722 atm. The results indicate that the highest coefficient of performance (COP) is 0.557 at t{sub g} = 60 C with cooling temperatures in the range 8--12 C. By using distillation calculations of the ideal system and the equilibrium relations concept of vapor-liquid systems, the enthalpy-concentration and temperature-concentration thermodynamic charts for the mixture are illustrated, saving time and effort for those making thermodynamic calculations. The influences of the various cycle temperatures on the COP and on the circulation ratio for this mixture have been performed. It is found that there is a minimum generation temperature above which operation of the cycle is possible, which is called the cut-in/cut-off temperature. Also, it is found that there is an optimum generation temperature at which a maximum value of COP is obtained. Lowering the condensing/absorbing temperature will lower both the minimum and optimum generating temperature and circulation ratio, which tends to reduce the required solar energy for heating the generator in addition to decreasing the pumping power. The effect of increasing the evaporator temperature has the same effect as lowering the condensing/absorbing temperature.

• Sponsoring Organization: USDOE
• OSTI ID: 562182
• Journal Information: Energy Sources, Journal Name: Energy Sources Journal Issue: 8 Vol. 19; ISSN 0090-8312; ISSN EGYSAO
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
ABSORPTION REFRIGERATION CYCLE
BUTANE
COEFFICIENT OF PERFORMANCE
HEPTANE
OPERATION
SOLAR AIR CONDITIONERS
TEMPERATURE DEPENDENCE
THERMODYNAMIC PROPERTIES
WORKING FLUIDS