GATE 2022 ME: RAC, PPE & IC Engines Quiz - 5

Which of the following statements are TRUE?

(a) Heat rejection ratio increases as evaporator temperature increases and condenser temperature decreases.

(b) Heat rejection ratio increases as evaporator temperature decreases and condenser temperature increases.

(c) For the same evaporator and condenser temperature, heat rejection ratio of open type compressor is small compared to hermetic compressors.

(d) The required size of condenser increases as heat rejection ratio decreases.

Which of the following statements are TRUE?

(a) Compared to water cooled condensers, the maintenance cost is low in air cooled condensers.

(b) Normally, systems with water cooled condensers operate at lower condensing temperature as compared to systems with air cooled condensers.

(c) The initial cost of water cooled condenser is high compared to air cooled condenser.

(d) all of above

Which of the following statements are correct with respect to expansion devices.

(a) It performs the thermodynamic function of expanding the liquid refrigerant from condenser pressure to evaporator pressure.

(b) Controls the supply of refrigerant to evaporator.

(c) It is a restriction offering resistance.

(d) All of above

In reciprocating compressor, clearance is provided

(a) To improve the volumetric efficiency of the compressor.

(b) To accommodate valves

(c) To account for thermal expansion due to temperature variation

(d) To reduce power consumption of compressor

Steam enters a turbine at 30 bar, 300 °C (u = 2750 kJ/kg, h = 2993 kJ/kg) and exits the condenser as saturated liquid at 15 kPa (u = 225 kJ/kg. h = 226 kJ/kg). Heat loss to the surrounding is 50kJ/kg of steam flowing through the turbine. Neglecting changes in kinetic energy and potential energy, the work output of the turbine (in kJ/kg of steam) is ________

A steam power plant operates on a theoretical reheat cycle as shown below. Steam enters high pressure turbine at 150 bar and 550 °C (h₃ = 3450 kJ/kg) and expands upto 40 bar (h₄ = 3050 kJ/kg). It is reheated at constant pressure of 40 bar to 550 °C (h₅ = 3560 kJ/kg) and expands through the low pressure turbine to a condenser at 0.1 bar (h₆ = 2300 kJ/kg). Also given, h_f1 (at 0.1 bar) = 191.8 kJ/kg.
Thermal efficiency (in %) and steam rate (kg/kWh) of the plant neglecting pump work respectively are: