Display cabinet heat exchanger design and sizing is carried out assuming a steady condition on both the refrigerant and the air side. In the case of evaporator feeding by Electronic Expansion Valves, this assumption can be reasonably accurate when step-motor valves are employed, while it deserves further investigations when Pulse-Width-Modulation (PWM) valves are used. Under this circumstance, in fact, the refrigerant is subject to sharp pressure gradients that propagate from the valve along the tubes, periodically disturbing the flow field. In the present paper, the effect of these unsteady phenomena on the expansion valve, distributor and evaporator system is studied. The time averaged performances of the evaporator installed in a commercial display cabinet using a PWM and a step-motor valve are compared under different operating conditions.
Impact of PWM Valve Unsteadiness on the performance of a Commercial Display Cabinet Evaporator
Paolo Artuso;Antonio Rossetti;Silvia Minetto;
2019
Abstract
Display cabinet heat exchanger design and sizing is carried out assuming a steady condition on both the refrigerant and the air side. In the case of evaporator feeding by Electronic Expansion Valves, this assumption can be reasonably accurate when step-motor valves are employed, while it deserves further investigations when Pulse-Width-Modulation (PWM) valves are used. Under this circumstance, in fact, the refrigerant is subject to sharp pressure gradients that propagate from the valve along the tubes, periodically disturbing the flow field. In the present paper, the effect of these unsteady phenomena on the expansion valve, distributor and evaporator system is studied. The time averaged performances of the evaporator installed in a commercial display cabinet using a PWM and a step-motor valve are compared under different operating conditions.
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