PH Enthalpy Chart and Refrigeration System D

26, the highest temp recorded on a PH Enthalpy chart

• superheated vapour at compressor inlet

• superheated vapour at compressor outlet

• saturated liquid at condenser outlet

• subcooled liquid at TEV valve inlet

27, when a refrigerant with zero glide, absorbs latent heat in the evaporator?

• refrigerant falls in temp

• temp of the refrigerant fluctuates

• rise in refrigerant temp

• refrigerant temp is constant

28, why an air cooled condenser is fitted with fins?

• to ensure smooth air flow

• make structure rigid

• to reduce noise and vibration

• to increase the heat transfer surface area

29, function of a compressor?

• to circulate oil

• cause a pressure difference

• keep constant condensing pressure

• keep compression ratio constant

30, increase in compressor discharge temp, reduction in mass flow rate, caused by

• leakage on pistons

• high ambient temp

• high suction superheat

• leak on comp reed valves

31, caused by increasing subcooling at the TEV

• refrigerant effect is reduced

• compressor WD is increased

• flash gas is reduced

• suction line superheat is increased

32, composition of Air at Sea level?

• 78% Nitrogen 21% Oxygen 1% CO2 + trace gases

• 70% Nitrogen 21% Oxygen 1% CO2 + trace gases

• 78% Nitrogen 16% Oxygen 4% CO2 2% CFC

• 70% Nitrogen 20% Oxygen 8% CO2 2% CFC

33, relationship between specific density of air sample and its specific volume?

• specific volume = 1 + specific density

• specific density = specific volume x gravity

• specific volume = specific density x 10-1

• specific density = specific volume divided by mass flow rate

34, why is there a difference between Wet and Dry Bulb temperatures

• wet bulb thermometer has lower internal pressure

• the moisture in the air is at a lower temperature

• wet bulb is measured in kelvin

• wet bulb thermometer is cooled by the evaporation of water

35, values of air at 15°C Dry bulb and 15°C wet bulb on a psychrometric chart

• A, 100% RH 0.86 m3/kg 43kj/kg

• B, 100% RH 20 m3/kg 42kj/kg

• C, 100% RH 20 m3/kg 43kj/kg

• D, 100% RH 0.83 m3/kg 42kj/kg