This paper describes the optimisation of water flow rate for a chilled-water heat transfer loop as a function of the air-water coil size and the refrigerant-water coil size. This problem has been successfully used as a case study in a senior-level design class. The optimisation problem is formulated in terms of dimensionless variables in order to reduce the number of independent design variables and to illustrate the general trends. The results show that for each possible heat exchanger selection, a finite optimal flow rate exists, which corresponds to a minimum temperature difference between the inlet air temperature and the evaporator temperature. The nondimensional model is then augmented by a specific set of boundary conditions (inlet temperatures, loads, or flows). The augmented model is then used to select the optimum design for a specific chilled-water heat transfer loop.

KEYWORDS: heat exchangers, air water heat exchangers, education, universities, designing, air conditioning, chillers, chilled water supply, cooler batteries, calculating, water flow.