Building Services Engineering 5th Edition Handbook

Ventilation and air conditioning 175
2. Thermostatic expansion valve allows refrigerant liquid to expand.
3. Opening of the thermostatic expansion valve is controlled from a temperature sensor
on the compressor discharge pipe.
4. Thermostatic expansion valve stops and starts the flow of refrigerant from a digital
controller.
5. TEV is an evaporator isolating valve.
82. Which of these correctly describes a water-cooled refrigeration system?
1. Cold vapour leaves the compressor and enters a finned tube heat exchanger with axial
flow cooling fans.
2. Low-pressure warm vapour condenses and rejects latent heat to the outside environment
through a shell and tube heat exchanger.
3. Refrigerant vapour condenses at 40 ◦ C in an air-cooled heat exchanger.
4. Water-cooled condenser pump circulates water to a cooling tower.
5. Refrigerant evaporator is a direct expansion cooling coil in an air-handling unit.
83. Which does a cooling tower do?
1. Always remains completely clean as it is continuously washed with water circulation.
2. Never polluted with airborne contamination.
3. Operates without any energy input.
4. Collects atmospheric dust, debris and bird droppings.
5. Filters the condenser cooling water.
84. Which is a primary characteristic of a cooling tower?
1. Quiet operation.
2. Uses almost no water.
3. Potential source of water-based Legionella bacteria for outdoor air.
4. Compact unit usually installed within a chiller plant room.
5. Functions equally well in any outdoor climate.
85. Which is a primary characteristic for absorption refrigeration?
1. Absorbs heat from within the building whereas a vapour-compression system cools a
water circulation system.
2. Has an absorption compressor.
3. Uses gas pressure to generate cooling.
4. Requires a source of primary heat energy.
5. Uses no electrical energy.
86. How is room ventilation rate measured?
1. Impossible to measure something that cannot be seen.
2. Can only be calculated from duct air flow rate measurement.
3. Found from releasing a non-toxic tracer gas into the room and measuring its rate of
decay with a katharometer.
4. Measured quantity of tracer gas concentration in room remains constant when
mechanical ventilation is switched off and measured with a thermo anemometer.
5. Tracer gas concentration measured with a carbon dioxide sensor and falls in a straight
line graph when mechanical ventilation is switched off.