Refrigeration Trade Theory N2 — Document

April 2020 — N2 — Refrigeration Trade Theory

N2 2020 Nated Engineering

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Q1— Section header —

1.1

1.2List FIVE m ethods of controlling the capacity of a compressor. (5\

1.3Make a neat labelled sketch of a rotating vane compressor.

1.4Briefly explain why a check or reed valve is installed in the discharge port of a rotating vane compressor

1.5Why is dryness a desirable property of refrigerant oil? (2\ [20]20

Q2— Section header —

2.1Draw a block diagram of a r efrigeration cycle and indicate the f ollowing: Compressor Condenser Liquid receiver Filter dryer Expansion valve

2.2What is the phase of the refrigeran t at the inlet and outlet of an evaporator? (2\ State FIVE requirements of a good refrigerant. (5\

Q3— Section header —

3.1Explain the purpose of each of the following and indicate where it is usually installed in systems

3.1.1Vibration eliminator

3.1.2Crankcase heater

3.1.3Strainer (9\

3.2Make a neat labelled sketch of a system analyser (manifold gauge set\ and indicate the following: High pressure gauge High pressure valv

Q4— Section header —

4.1State FOUR precautions to follow when using a swaging tool. (4\

4.2State FIVE safety precautions to apply when working with refrigerants. (5\

4.3Define each of the following refrigeration control terms:

4.3.1Hunting

4.3.2Cycling (4\

4.4What is the result of liquid slugging in refrigeration systems? (2\

4.5Name T WO types of oil used in refrigeration systems. (2\

4.6Which type of fan would be installed in a large air conditioning plant? Give TWO reasons for the answer

Q5— Section header —

5.1Which THREE facts should be kept in mind when designing refrigeration piping? (3\

5.2Briefly explain why a muffler would be installed in a refrigeration system. (3\

5.3here is the muffler in a refrigeration system installed? (1\

5.4Briefly explain the cause of each of the following malfunctions on a hermetically sealed unit

5.4.1Motor humming when switched on

5.4.2Suction line frosted or sweating

5.4.3Thermostat switches on but motor fails to start (6\

5.5Briefly explain FIVE possible reasons why the suction superheat reading will too high. (5\

5.6Give TWO uses of a service manifold. (2\ [20] TOTAL:20

Mark Allocation

Sections20 + 20 + 20 + 20 + 20 = 100 marks

Paper information

TitleDocument

SubjectRefrigeration Trade Theory

LevelN2

Document typeQuestion paper

Year2020

MonthApril

Pages6

Downloads4

Examination context

Decade2020s

Years ago6y

SeasonAutumn (SH)

Start dayWednesday

Exam periodApril 2020

Days since exam2,384

About Refrigeration Trade Theory examination preparation

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