This paper introduce a transient model of the propane heat pump cycle. The heat pump cycle model includes: a compressor model, a condenser model in lumped parameters, an evaporator model in lumped parameters, an expansion valve model, a heat source model (cooling chamber), a PID control system for heat recovery from superheated refrigerant vapour. The model allows estimate inertia of the heat pump cycle with the system of the heat recovery from superheated propane vapor. The presented theoretical model can determine unsteady and steady state conditions of the different subsystems in the heat pump cycle (condenser, evaporator, compressor). The article presents the results of calculations and determines the time of reaching steady states of the key systems of the heat pump system. The article also presents (in a graphical form) the behavior of the system where the setting was changed after reaching the steady state after 2000s from 50kW to 40kW at the thermal load of the additional heat recovery exchanger.
The paper presents the calculations for the failure conditions of the ORC (organic Rankine cycle) cycle in the electrical power system. It analyses the possible reasons of breakdown, such as the electrical power loss or the automatic safety valve failure. The micro-CHP (combined heat and power) system should have maintenance-free configuration, which means that the user does not have to be acquainted with all the details of the ORC system operation. However, the system should always be equipped with the safety control systems allowing for the immediate turn off of the ORC cycle in case of any failure. In case of emergency, the control system should take over the safety tasks and protect the micro-CHP system from damaging. Although, the control systems are able to respond quickly to the CHP system equipped with the inertial systems, the negative effects of failure are unavoidable and always remain for some time. Moreover, the paper presents the results of calculations determining the inertia for the micro-CHP system of the circulating ORC pump, heat removal pump (cooling condenser) and the heat supply pump in failure conditions.
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