Page 67 - Low Temperature Energy Systems with Applications of Renewable Energy

56 Low-Temperature Energy Systems with Applications of Renewable Energy

Fig. 2.4 Schematic of using soil water with aggressive properties: see Fig. 2.2 for terms; 9, heat
exchanger; 10, glycol circulating pump.
feasibility should be estimated accounting for physical characteristics of heat ex-
changers. When common heat exchangers are used, one can use a scheme with an in-
termediate circuit [5], shown in Fig. 2.5. In that case, water from the pond is fed with a
submerged pump 9 into the heat exchanger 7 and drained back into the pond. In the
intermediate circuit filled with glycol, heat is transferred from the heat exchanger
into the heat pump evaporator 2.
Fig. 2.6 illustrates a system without the intermediate circuit [5]. In such a case,
thermal energy of the water is taken by means of a coil made from cross-linked poly-
ethylene tubing submerged into the pond; the coil may be compact (Fig. 2.6) or large-
scale (Fig. 2.7).
To determine the length of the polyethylene pipe, one can use the following equa-
tion [5]

L ¼ C Dt m (2.2)

Fig. 2.5 Schematic of using an open pond with an intermediate circuit: 1, heat pump
compressor; 2, evaporator; 3, condenser; 4, heating system; 5,6, circulating pumps; 7, heat
exchanger; 8, filter; 9, submerged pump.