CYCLE_D-HX: NIST Vapor Compression Cycle Model Accounting for Refrigerant Thermodynamic and Transport Properties

CYCLE_D-HX simulates the performance of single-compound refrigerants and refrigerant blends in subcritical vapor-compression refrigeration cycles. The basic system simulated by CYCLE_D-HX consists of a compressor, discharge line, condenser, expansion device, evaporator, compressor suction line, and an optional liquid-line/suction-line heat exchanger.  The other cycles may contain a second compressor, one or two economizers, or an intercooler. 

In contrast to simplified vapor compression cycle which require refrigerant saturation temperatures in the evaporator and condenser as input, CYCLE_D-HX establishes saturation temperatures in the heat exchangers using the temperatures profiles of heat source and heat sink and the mean effective temperature differences in the evaporator and condenser, respectively, which are specified as input to the program. This representation of heat exchangers facilitates the inclusion of both thermodynamic and transport properties in cycle simulations and makes CYCLE_D-HX suitable for comparative evaluations of different refrigerants, particularly when applied in systems relying on forced-convection heat transfer of refrigerant in the heat exchangers. The program includes the option to optimize refrigerant circuitry in the heat exchangers to maximize the system coefficient of performance.

CYCLE_D-HX includes 70 single-compound refrigerants and 97 predefined blends. Single-compound fluids can be combined to form blends of up to five components. Computationally, the program is fully compatible with the NIST Reference Fluid Thermodynamic and Transport Properties - REFPROP, Version 9.1.

CYCLE_D-HX graphical user’s interface includes pull-down help menu and several options for reviewing simulation results, including pressure-enthalpy and temperature-entropy diagrams.