Since it was possible to determine a reference value for the control system, a series of tests were performed in order to evaluate refrigeration performance at different engine speeds. Table 1 summarizes the test conditions which were employed. All experiments listed in Table 1 were conducted for 1 h. The basic test parameters are engine speed, which controls the temperature of the exhaust gases, and engine torque, which is positively related to the
flow speed of the exhaust gases. Thus, by increasing both engine throttle and torque, the amount of heat present in the exhaust gases is also increased. The behaviour of the control system, represented by valve opening values (V1 and V2) as well as TG is presented in Fig. 4, while the evolution of TE over time is shown in Fig. 5.