1. Choose the correct answer from the given four alternatives:

When air is adiabatically saturated, the temperature attained is

dew point temperature

dry bulb temperature

wet bulb temperature

triple point temperature

Wet bulb depression represents the difference between

dry bulb temperature and wet bulb temperature

dry bulb temperature and dew point temperature

dew point temperature and saturation temperature

adiabatic saturation temperature and dew point temperature

For a given dry bulb temperature as the relative humidity decreases, the wet bulb temperature will

increase

decrease

be the same

depend on other factors

The saturation temperature at the partial pressure of water vapour in the air-water vapour mixture is called

dry bulb temperature

wet bulb temperature

dew point temperature

saturation temperature

In an ideal refrigeration (reversed Carnot) cycle, the condenser and evaporator temperatures are 27°C and -13°C respectively. The COP of this cycle would be

6.5

7.5

10.5

15.0

Vapour absorption refrigeration system works using the

ability of a substance to get easily condensed or evaporated

ability of a vapour to get compressed or expanded

affinity of a substance for another substance

absorptivity of a substance

In a vapour compression system, the working fluid is superheated vapour at the entrance to

evaporator

condenser

compressor

expansive valve

2. Answer any two of the following:

Explain vapour compression refrigeration system with the help of a block diagram.

What is refrigerating effect? Show that the COP of a heat pump is greater than the COP of a refrigerator by unity.

A domestic food freezer maintains a temperature of -15°C. The ambient air temperature is 30°C. If heat leaks into the freezer at the continuous rate of 1.75 kJ/sec., what is the least power necessary to pump this heat out continuously?

Derive the expression for the maximum COP of a vapour absorption refrigeration system.

What do you understand by dry bulb temperature and wet bulb temperature Also define dew point temperature.

Explain the concept of defrosting. How is defrosting achieved in a domestic refrigerator?

Explain the advantages of central air-conditioning system over unitary air-conditioning system.

Why is transport refrigeration necessary List the commodities (items) preserved during transport refrigeration.

A Carnot refrigerator requires 1.3 kW per tonne of refrigeration to maintain a region at low temperature of -38°C.

Determine:

COP of the Carnot refrigerator

Higher temperature of the cycle

5. Write short notes on any four of the following:

Secondary Refrigerants

Depletion of Ozone Layer

Specific Humidity

Relative Humidity

Air Filter

Desirable Properties of Refrigerants