Control and optimization of central chilling systems - Intelligent Buildings and Building Automation - page 184

Condenser water

Condenser

High pressure side

Motor

Low pressure side

Expansion
valve

Compressor

Evaporator

Chilled water

Figure 9.6 Schematic diagram of a water-cooled chiller system.

Condensing

Differential
pressure

Increasing
COP

Evaporating

h1 h2

h4 Enthalpy

Figure 9.7 Pressure-enthalpy diagram for an ideal refrigeration cycle.

is significantly less than that obtained from the theoretical calculation.
Normally, a saving of 1.5-2.5 per cent can be expected by reducing the
condensing temperature by 1 K or increasing the evaporating temperature
by 1 K in practical chillers at normal air-conditioning conditions. There is
also a minimum condensing temperature limit for chillers which varies due
to different chiller designs. The evaporating temperature should be as high as
possible, which is determined by the specific requirements and the working
conditions of the air-conditioning terminal units.