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Air/Water Heat Exchangers

The air/water heat exchanger is a thermal component which allows transferring energy between the fluid in the loop and the ambient air. Heat transfer can go in both directions: from the fluid in the loop to the ambient air or from the ambient air to the fluid in the loop. Therefore, the ambient air can be a heat source or a heat sink. No additional settings are required to change heat flow direction through the heat exchanger. Depending on the temperature of the fluid entering the heat exchanger and the temperature of the ambient air, the component defines itself the direction of the heat transfer. The air/water heat exchanger can be used with different technologies: water-water heat pumps, compressor- and thermal-driven cooling machines.  

Figure: dialog window of the air/water heat exchanger

The air/water heat exchanger is computed using the well-known “Number of Transfer Units (NTU) – Effectiveness” method. The method works as follows: based on design (nominal) values of the heat exchangers (transfer power capacity, temperature differences and flow rates at both sides) the UA-value is calculated => each time-step NTU, effectiveness and maximum theoretical transfer power capacity are defined => based on these values operational transfer power capacity is found=> having transfer power capacity outlet temperatures at both sides of the heat exchanger can be determined. The air/water heat exchanger is adiabatic. It means there is no heat transfer with ambient environment through the heat exchanger enclosure. The latent heat in the air is not considered in the model.