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Intracycle Evaporative Cooling in a Vapor Compression Cycle (NISTIR 5873)



B. S. Kim, Piotr A. Domanski


The temperature glide of zeotropic mixtures during phase change provides the opportunity to limit throttling losses of the refrigeration cycle by intracycle evaporative cooling of the refrigerant leaving the condenser. Intracycle evaporative cooling is similar to the use of a liquid-line/suction-line heat exchanger with the difference that a two-phase low-pressure refrigerant, instead of superheated vapor, is used to subcool the high-pressure liquid leaving the condenser. Intracycle evaporative cooling was evaluated by a semi-theoretical simulation model and experimentally in an instrumented laboratory heat pump at the cooling mode operating condition typical for a water-to-water residential heat pump. The capacity, coefficient of performance (COP), pressures, and temperature profiles of refrigerant and heat-transfer fluid in the heat exchangers are reported. The laboratory measured improvement of the COP was 4.0% for R32/152a, 3.6% for R407C, and 1.8% for R23/152a.
NIST Interagency/Internal Report (NISTIR) - 5873
Report Number


cooling, air conditioning, building technology, coefficient of performance, heat pumps, refrigeration, zeotropic mixtures


Kim, B. and Domanski, P. (1996), Intracycle Evaporative Cooling in a Vapor Compression Cycle (NISTIR 5873), NIST Interagency/Internal Report (NISTIR), National Institute of Standards and Technology, Gaithersburg, MD, [online],, (Accessed June 19, 2024)


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Created August 31, 1996, Updated October 12, 2021