Page 96 - Low Temperature Energy Systems with Applications of Renewable Energy

Characteristics of low-temperature energy sources for heat pumps 85

The required compressor power is

Q 0 ¼ 20:0 4:9 ¼ 15:1kW

The length of the collector pipes is

15100 3:5 1
L ¼ ¼ 568 m
19:0 3:5
For the construction of a ground collector, three 190 m long loops are
required.
The required area of the site to accommodate the collector is

n 1
A ¼ L a
n
3 1 2
A ¼ 568 0:75 ¼ 284 m
3

Vertical collector
The specific heat flow from the soil to the pipes of the vertical collector is

q 0 ¼ 1:2½ð1:4 1:61Þ 0:5Šð0:4 þ 1Þð8 0Þ¼ 23:5W=m

The length of vertical manifold pipes is

15100 3:5 1
L ¼ ¼ 459 m
23:5 3:5
We accept the collector design of five wells, each with a depth of 92 m.

Exercises

1. Determine the length of a horizontal ground heat exchanger for a heat pump with a capacity
of: A: 25 kW; B: 10 kW. The heat exchanger is laid in soil consisting of clay with a moisture
content of 10%; the soil temperature at a depth of 2 m is 5 C.

2. Determine the length of the vertical ground heat exchanger for a heat pump: A: 250 kW; B:
100 kW. Geological data: at a depth of up to 100 m, the soils are represented by sand with a
moisture content of 5%; soil temperature is 10 C.

3. Determine the coefficient of performance of a heat pump system with a ground heat
exchanger. The heating system is radiant floor heating. R410a (Case A) and R407a (Case
B) are used as heat pump working fluids.