A transfer function to model a direct expansion air cooled evaporator, inse
rted in a vapor compression refrigeration plant, is deduced by means of exp
erimental analysis. For inlet air temperatures onto the evaporator and refr
igerant mass flow rate variable in appropriate ranges, the evaporator dynam
ic behavior is simulated by a linear model with delay. The results of trans
fer function are compared with experimental data, obtained by applying both
step inputs and periodic changes to the refrigerant mass flow rate. The in
fluence of the hunting, typical of a thermostatic expansion valve, is also
estimated experimentally and then validated by the transfer function, obtai
ning a good agreement. These results could be applied to obtain a control a
lgorithm for the refrigerant mass flow rate feeding the evaporator, by vary
ing the speed of the compressor motor. (C) 2000 Elsevier Science Ltd. All r
ights reserved.