Impact of an internal heat exchanger on a transcritical CO2 heat pump under optimal pressure conditions

Numerical performance of a water source transcritical CO2 heat pump with mechanical subcooling

“…A is the base CO 2 cycle with IHX and without DMS. This configuration is taken as a reference to evaluate the interest in employing a DMS system and corresponds to the one previously studied by the authors in previous works [3,4,32,33]. The numerical model used for this configuration has been already validated under different operating both in stationary and transient conditions [3,4,32,33].…”

“…All main components of both, the auxiliary and the main cycle, have been modeled and included in a numerical model of the coupled system. The components of the main cycle included in the model are those that actually form part of the experimental facility described in previous works [3,4,32,33]. The components of the auxiliary R1234yf cycle have been selected using their respective manufacturer's selection software in order to design an auxiliary cycle that can be coupled to the existing main cycle.…”

“…In order to obtain the correlations that describe the behavior of each heat exchanger, two different approaches have been used. The approach used to model all the heat exchangers of the main CO 2 cycle is the same used in previous works [4,33]. It consists of a 1D cell-by-cell discretization method that divides the heat exchanger into n cells, applies the energy conservation equation to each cell, and solves iteratively until convergence in the heat transfer area is reached; further details of this method can be found in [33].…”

“…The approach used to model all the heat exchangers of the main CO 2 cycle is the same used in previous works [4,33]. It consists of a 1D cell-by-cell discretization method that divides the heat exchanger into n cells, applies the energy conservation equation to each cell, and solves iteratively until convergence in the heat transfer area is reached; further details of this method can be found in [33]. On the other hand, since the condenser of the auxiliary R1234yf cycle is a conventional water/subcritical refrigerant plate heat exchanger, a well-known commercial software, IMST-ART [40], extensively used by several authors in their research work [41][42][43][44][45][46] as a simulation tool to model refrigeration cycle components, including different types of heat exchangers, has been used to obtain condensation pressure and heat transfer rate.…”

Evaluation of the Use of Different Dedicated Mechanical Subcooling (DMS) Strategies in a Water Source Transcritical CO2 Heat Pump for Space Heating Applications

“…Previous investigations have shown that the coefficient of performance (COP) of water source transcritical CO 2 heat pumps is high, especially when the inlet water temperature to be heated is low, whereas it decreases when the inlet water temperature increases as in the case of space heating applications [2,3,[22][23][24]. In fact, as the inlet temperature of the water to be heated increases, the enthalpy of the refrigerant at the exit of the gas cooler also increases, which reduces the enthalpy downstream the isenthalpic expansion valve of the heat pump and, therefore, reduces the specific heat absorbed at the evaporator, which also reduces the heat transferred at the gas cooler by the heat pump [24].…”