Page 177 - Low Temperature Energy Systems with Applications of Renewable Energy

Heat pumps in the drying industry 167

Greek letters

a bypass ratio
h operational efficiency
h ex exergy COP
n volume
x concentration
4 relative humidity

Subscripts

DA drying agent
dc drying chamber
DP dryer plant
GHG greenhouses gas
HP heat pump
HPDP heat pump dryer plant
MC mixing chamber
PC psychrometric chart
SEC specific energy consumption
SMER amount of moisture evaporated

Review questions

1. Describe the types of heat pump dryers according to the scheme of implementation of the
drying process.
2. Name the conditions for effective usage of the heat pump in a dryer plant.
3. Give the classification of heat pump dryers.
4. Describe the criteria of efficiency for using heat pumps in drying plants.
5. Discuss the main reasons for using heat pumps in drying technology in the 20th century.
6. Name the auxiliary sources of heat energy when operating heat pump dryers.
7. Name the prerequisites for the use of heat pumps in the processes of drying grains.
8. Name the functions of the heat pump in the grain drying plants of different systems.
9. (A) What determines the efficiency of heat pump grain dryers and (B) what is the effective-
ness of their use compared to traditional systems.
10. In what modes of drying wood it is expedient to use a heat pump?
11. Describe the types and designs of heat pump dryers of wood.

Example

Determine the parameters at the characteristic points of the process and construct
the process in the enthalpy-concentration (h, x) diagram. Find the heat loads of the
apparatus, the specific energy consumption, the refrigerating coefficient, and the
exergy efficiency of the plant (Fig. 4.E1 and Tables 4.E1 and 4.E2).