IEA Solar Heating and Cooling Programm - NachhaltigWirtschaften.at

IEA SHC Task 38 Solar Air Conditioning and Refrigeration Subtask C2-A, November 9, 2009
With reference to Figure 1, the conventional cycle operates as follows: outside air (1) is
dehumidified in a desiccant wheel (2); it is then cooled in the sensible regenerator (3) by the
return cooled air before undergoing another cooling stage by evaporation (4) and being
introduced into the building. The operating sequence for the return air (5) is as follows: it is
cooled to its saturation temperature by evaporative cooling (6) and then it cools the fresh air
in the rotary heat exchanger (7). It is then heated in the regeneration heat exchanger by solar
energy (8), it regenerates the desiccant wheel (9) by removing the humidity and exits the
installation.
Modelling of the components
Sensible regenerator
A sensible regenerator is a porous matrix which passes periodically between a hot and a
cold stream. The cellular matrix of the regenerator stores heat from the hot gas stream and
releases it to the cold gas stream.
Heated air
stream
Cold air
stream
T 7
T 6
Hot air
stream
Cooled air
stream
T 2
T 3
Figure 2: Sensible heat regenerator principle
For modelling purposes, the following assumptions are made:
• Heat transfer between air and the regenerator matrix is considered using a lumped
transfer coefficient or a number of transfer units (NTU)
• The channels where the fluid flows are identical and parallel
• No leakage occurs between the air streams
The heat conservation and transfer governing equations, after Kays and London [6] and
Maclaine-cross and Banks [7], are:
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