Hardware-in-the-Loop Load Emulation for Air-Conditioning and Refrigeration Systems

This paper presents a novel approach for experimentally simulating various environmental conditions and container parameters on air conditioning and refrigeration (AC&R) systems. The proposed emulation technique uses a hardware-in-the-loop (HIL) system to simulate the loading conditions on the evaporator during experimental testing. The evaporator air inlet conditions are controlled with a small emulation unit attached to the evaporator, analogous to a dynamometer attached to an engine for laboratory testing. An on-line real time model, with the parameters of the container being simulated, is used to determine the virtual container temperature. The emulation unit then tracks this virtual container temperature by mixing the proper amount of evaporator output air with ambient air. The online model takes in measurements from the experimental system to determine the cooling rate of the virtual container. Load emulation ultimately allows for a flexible testing environment without the need for full size test chambers or containers.