Active Thermal Cooling Technologies - Low Energy Cooling for Sustainable Buildings - page 168

Figure 5.56 View of the second prototype with its components

bubble pump was developed and the auxiliary gas circuit was constructively reworked
to reduce pressure drops. These changes resulted in a weight reduction down to 290 kg
and a height reduction down to 2.40m (see Figure 5.56) which are important factors
for a more marketable unit. The second prototype went into operation in July 2003
and ran until July 2005.
Measuring results of stationary temperature, pressure and capacity levels were taken
by varying the heating temperatures, the cooling water temperatures and the cold brine
temperatures. The heating temperature range of the generator was reduced from 150
to 175 ◦ C for the first pilot plant to 110 to 140 ◦ C for the second pilot plant. This
is due to the decreased lifting height of the bubble pump by a half. Combined with
an appropriate heat transfer surface, the efficiency of the bubble pump increased and
temperature levels dropped.
The continuous evaporator cooling capacities of the first measurements from July
2003 to November 2003 evaluated at an operating pressure of 18

10 5 Pa were around
0.5 kW with COPs between 0.1 and 0.2. The maximum cooling capacity reached was
0.8 kW.

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Solution Heat Exchange The plate SHX was replaced by a coaxial SHX due to the
very low heat recovery factors of 11.4% and 31.2% for the rich and weak solution sides
respectively. The heat recovery factors of the coaxial heat exchanger of prototype 2