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## How to Prepare Refrigeration and Air- Conditioning For GATE|| important topics

Refrigeration and Air- Conditioning is a significant topic from GATE perspective.

Our experts have devised this article so as to help our readers learn on the strategy to prepare for Refrigeration and Air- Conditioning section of GATE 2017.

This article will cast light on the important sub-topics to prepare under Refrigeration and Air-Conditioning section of GATE Mechanical 2017.

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## Important Topics from Refrigeration and Air-Conditioning/ What to Prepare for GATE 2017

Air Conditioning || Important topics for GATE 2017

• You must have a general idea of the basic working of Air Conditioning system and the types of Air-Conditioning systems
• You must prepare Psychrometric charts with due emphasis on numerical part.
• You must thoroughly study various Psychrometric processes and Cycles
• You must lay a lot of emphasis on practicing numerical questions under psychrometric processes and psychrometric charts as they are very important from examination perspective

Refrigeration || Important Topics for GATE 2017

• You must have an overview of the basic working of Refrigeration system and various types of refrigerants.
• Study topics like Vapour refrigeration cycle, heat pumps, gas refrigeration and Reverse Brayton cycle in depth as they are really important under this section
• Practice a variety of numericals on various topics listed above as numericals carry a lot of weight age in GATE exam

## Solved Questions from Previous GATE Papers

Question :

A vapour absorption refrigeration system is a heat pump with three thermal reservoirs as shown in the figure. A refrigeration effect of 100 W is required at

250 K when the heat source available is at 400 K. Heat rejection occurs at 300 K.

The minimum value of heat required (in W) is

1. 167
2. 100
3. 80
4. 20

Solution :

( COP)ref  = Refrigeration Effect / Work Done = T1/ (T2 - T1 )

100/W = 250/(300-250)

W = 20 watt

For supply this work, heat is taken from reservoir 3 & rejected to sink 2.

So efficiency,

Efficiency = W/ Q3 = (T3 – T2)/ T3           (It works at heat engine)

T3 = 400

So , Q3 = 80 Watt

Hence c

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GATE-2017 Preparation

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Question :

Moist air at a pressure of 100 kPa is compressed to 500 kPa and then cooled to 35 degree C in an aftercooler. The air at the entry to the aftercooler is unsaturated and becomes just saturated at the exit of the after cooler. The saturation pressure ofwater at 35 degree C is 5.628 kPa The partial pressure of water vapour (in kPa) in the moist air entering the compressor is closest to

(A) 0.57

(B) 1.13

(C) 2.26

(D) 4.52

Solution :

Best Wishes !!