Design and Simulation Methods for Evaporators with Zeotropic Refrigerant Mixtures

Zeotropic mixtures, whose components have different mass fractions in the liquid and vapor phases at equilibrium conditions such as R407C, ammonia with traceable water and R-134a mixed with Mobil Arctic EAL 68 lubricating oil, are found in various HVAC and refrigeration systems. These mixtures evapo...

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Bibliographic Details
Published in:ASHRAE transactions 2015-01, Vol.121, p.1LL-1LL
Main Authors: Zhong, Yongfang, Glanville, Paul, Garrabrant, Michael, Stout, Roger
Format: Article
Language:English
Subjects:
Alternative energy sources
Ammonia
Design
Design engineering
Evaporators
Fluids
Heat exchangers
Heat transfer
Lubrication
Methods
Nonlinearity
Quality
Refrigerants
Refrigeration
Simulation
Temperature
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Summary:Zeotropic mixtures, whose components have different mass fractions in the liquid and vapor phases at equilibrium conditions such as R407C, ammonia with traceable water and R-134a mixed with Mobil Arctic EAL 68 lubricating oil, are found in various HVAC and refrigeration systems. These mixtures evaporate over a temperature range, resulting in a non-linear temperature-enthalpy relationship. The nonlinear relationship makes the assumption underlying widely-used log mean temperature difference and effectiveness-NTU methods invalid. This paper demonstrates simulation and design errors that can result from the application of the standard method. The standard method is also found to undersize the evaporator with ammonia-water as refrigerant. A simple energy balance method is used as an alternative solution. The results from this method have good agreement with experimental data and it may be applied to the simulation and design for heat exchangers with zeotropic refrigerant mixtures.
ISSN:0001-2505