Recovery of heat from water source at medium temps. - using heat pumps and heat exchangers in a closed loop circulating system

摘要

Water coming from a heating network is first cooled by passing it through the evaporation side of a series of one or more heat pumps, then passed through a series of one or more heat exchangers, where it is heated by the medium temp. water source that flows through the exchangers and back to its origin, then further heated by passing through the condensing side of the heat pumps before returning to the heating network. The number of heat pumps is established by keeping the temp. difference between the liq. on the hot and cold sides to a max. of 40 degrees C and the number of heat exchangers determined by the average logarithmic temp. difference at the hot end to the temp. difference at the cold end. A by-pass pipe takes a proportion of the water from the heating network from upstream of the first heat pump to rejoin the flow downstream of the first heat exchanger, the quantity of water passing through the heat pump evaporators being at least equal to that of the heat source. The heat recovery water circuit also has supplementary by-passes parallel to the evaporators and condensers of each heat pump and also in parallel to the exchangers so that flow through them can be adjusted. A further by-pass connects the by-pass around the heat pumps and first exchangers to by-pass around the heat pump condensers. A boiler can be placed between the outlet of the first heat pump condenser and the return to the heating network to supply additional heat. For recovery of heat from medium temp. sources, e.g. recovering heat from geothermal waters for central heating circuits. Gives a max. recovery of heat using current plant items and the cost of maintenance, construction and operation is reduced.