Page 93 - Low Temperature Energy Systems with Applications of Renewable Energy

82 Low-Temperature Energy Systems with Applications of Renewable Energy

Dt ev temperature difference between heat pump surroundings and working fluid at
evaporator outlet
temperature difference between air at the evaporator inlet and outlet
Dt a
Dt c temperature difference between heat pump working fluid and water at
condenser outlet
Dt io fluid temperature difference at soil collector input and output
Dt w water temperature difference at evaporator inlet and outlet
V fan
V a volume fan loss
V s volume loss
W c and W w amount of cooling and heating used per year
WP water pipe

Greek symbols
h m:e and h efficiency of ambient coolant driver and its motor, respectively
s dr
h HP efficiency accounting for real processes of the heat pump working fluid
l heat conductivity
r f fluid density
r s surrounding density
4 calculated COP
4 t theoretical heat pump COP

Review questions

1. Discuss the problems of using ambient air in typical winter conditions in the northern
hemisphere.
2. Discuss the characteristics of ventilation wastes and their use in domestic and municipal
buildings.
3. What air velocities should be assumed in the “air-air” type heat pumps?
4. Which ventilation wastes from a building can be used in heat pumps? What ventilation fre-
quencies are appropriate for different building purposes? What are the advantages and dis-
advantages of the heat pumps of “ventilation air-water” type?
5. What system of heating devices is used with heat pump heating supply?
6. What are the peculiarities of using ventilation air from mines and metropolitan infrastructure
in heat pumps?
7. What are the requirements for well siting when using artesian waters?
8. Describe the construction of the heat collector using open pool water.
9. What are the advantages and problems of using the heat of sewer waters in heat pumps?
10. How may the heat of turbine condensers be used? Include a discussion of efficiency values.
11. In what cases is it desirable to use the recycled water from district heating networks in heat
pumps?
12. What are the advantages of using a heat pump instead of alternative systems?
13. Explain the designs of vertical and horizontal soil heat exchangers.
14. Explain the principle of using the heat of solidification of water (i.e., phase transition from
liquid to solid) for air heating. Give the value of water crystallization heat.