How heat recovery chillers work

A heat recovery chiller is a traditional screw type chiller where the heat of condensing is absorbed by a water loop, which is then used for heating.  Typically, the temp of the water produced by the heat recovery chiller is not high enough to do stand alone heating, and the higher the temp of water produced by the condenser, the lower the efficiency of the refrigeration side of the system (a higher kW/ton will be needed to produce chilled water).  So a heat recovery chiller is best utilized in a lower design temp, larger delta T heating system, where the condensing water heat can be used to pre-heat the return water from the heating loop (prior to going through the boiler).  The main requirement for using heat recovery chillers in a way that saves energy is that the building has a year-round cooling and heating load. Considering only the water chilling mode, a heat recovery chiller is not that efficient (0.75-0.9 kw/T vs. 0.6 or lower for a typical centrifugal chiller). It’s only the production of chilled water with the ancillary production of heat which makes this a good technology to reduce the site EUI (energy use intensity). Also, the heat recovery chiller should be base loaded, i.e. the first chiller in line to be used for chilled water. The more loaded the chiller is, the better the system EER, a parameter which factors in how much energy is used to produce the total energy out compared with the total energy in. The goal with a heat recovery chiller is to operate it such that the maximum EER is achieved for the maximum amount of time. This will only be possible for a building which has a year-round heating and cooling load which match the full capacity of the chiller.

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