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SOUTH AFRICAN QUALIFICATIONS AUTHORITY

REGISTERED UNIT STANDARD THAT HAS PASSED THE END DATE:

Analyse the refrigeration cycle with the air of the Pressure Enthalpy diagram and refrigerant tables

SAQA US ID	UNIT STANDARD TITLE
9457	Analyse the refrigeration cycle with the air of the Pressure Enthalpy diagram and refrigerant tables
ORIGINATOR
SGB Air-conditioning Refrigeration and Ventilation
PRIMARY OR DELEGATED QUALITY ASSURANCE FUNCTIONARY
-
FIELD			SUBFIELD
Field 06 - Manufacturing, Engineering and Technology			Engineering and Related Design
ABET BAND	UNIT STANDARD TYPE	PRE-2009 NQF LEVEL	NQF LEVEL	CREDITS
Undefined	Regular	Level 5	Level TBA: Pre-2009 was L5	7
REGISTRATION STATUS		REGISTRATION START DATE	REGISTRATION END DATE	SAQA DECISION NUMBER
Passed the End Date - Status was "Registered"		2001-06-13	2004-06-13	SAQA 0836/01
LAST DATE FOR ENROLMENT		LAST DATE FOR ACHIEVEMENT
2005-06-13		2008-06-13

In all of the tables in this document, both the pre-2009 NQF Level and the NQF Level is shown. In the text (purpose statements, qualification rules, etc), any references to NQF Levels are to the pre-2009 levels unless specifically stated otherwise.

This unit standard does not replace any other unit standard and is not replaced by any other unit standard.

PURPOSE OF THE UNIT STANDARD

Plot the thermodynamic cycle of single and multi stage refrigeration systems on a pressure-enthalpy diagram to determine the operating parameters of the system and detect possible reasons for inefficient or ineffective performance of the system.

LEARNING ASSUMED TO BE IN PLACE AND RECOGNITION OF PRIOR LEARNING

An understanding the operation of vapour compression refrigeration systems
Convert operating parameters from the imperial or metric system to the SI system or vice versa.

UNIT STANDARD RANGE

Single and two stage plants including those incorporating economisers and/or liquid/suction line heat exchangers.

Specific Outcomes and Assessment Criteria:

SPECIFIC OUTCOME 1

Obtain all information required.

ASSESSMENT CRITERIA

ASSESSMENT CRITERION 1

1. Information required is obtained or requested.

ASSESSMENT CRITERION 2

2. Observations are acceptable.

ASSESSMENT CRITERION 3

3. Information is in the correct SI units or converted correctly.

ASSESSMENT CRITERION 4

4. The correct SI symbols and units are used.

ASSESSMENT CRITERION 5

5. The consequences of inaccurate readings or faulty conversions are listed and explained.

SPECIFIC OUTCOME 2

Plot the refrigeration cycle on the Pressure-Enthalpy diagram and determine refrigerant properties.

ASSESSMENT CRITERIA

ASSESSMENT CRITERION 1

1. The pressure-enthalpy diagram for the correct refrigerant in the correct units is selected.

ASSESSMENT CRITERION 2

2. All parameters are plotted correctly.

ASSESSMENT CRITERION 3

3. The refrigerant properties are determined correctly from the diagram or tables.

ASSESSMENT CRITERION 4

4. The correct SI units and symbols are used.

SPECIFIC OUTCOME 3

Analyse the refrigeration cycle.

ASSESSMENT CRITERIA

ASSESSMENT CRITERION 1

1. The enthalpy differences in the components are determined correctly.

ASSESSMENT CRITERION RANGE

Refrigerating effect, heat of compression and heat rejection.

ASSESSMENT CRITERION 2

2. The system operation is analysed correctly and the values obtained are compared with accepted norms.

ASSESSMENT CRITERION RANGE

Superheat, sub cooling, co-efficient of performance, compressor efficiency, compression ratio.

ASSESSMENT CRITERION 3

3. The effects of including an economiser or a heat exchanger on the performance of the plant are explained.

ASSESSMENT CRITERION 4

4. The effects of varying operating parameters on equipment selection on plant performance are explained.

ASSESSMENT CRITERION NOTES

Increase or decrease in suction and discharge pressure, over sizing or under sizing of components or accessories, increasing or decreasing evaporator or condenser approach, increasing or decreasing the fluid quantities through the condenser or the evaporator, over or undercharge of refrigerant, inclusion of an economiser and/or a liquid/suction line heat exchanger.

ASSESSMENT CRITERION 5

5. The effect of refrigerant glide are explained and discussed.

SPECIFIC OUTCOME 4

Calculate the heat balance of the system.

ASSESSMENT CRITERIA

ASSESSMENT CRITERION 1

1. The refrigerant mass flow and volume flow are determined correctly.

ASSESSMENT CRITERION 2

2. The capacities and operating parameters of the components are determined correctly.

ASSESSMENT CRITERION RANGE

Capacity of evaporator, TEV, condenser and compressor.

ASSESSMENT CRITERION 3

3. The power input into the system is calculated.

ASSESSMENT CRITERION RANGE

Input to motor, gearbox and compressor.

ASSESSMENT CRITERION 4

4. The heat balance of the system is calculated and evaluated.

ASSESSMENT CRITERION 5

5. Possible reasons for an unacceptable heat balance are explained.

ASSESSMENT CRITERION 6

6. The system performance is explained and discussed.

SPECIFIC OUTCOME 5

Evaluate the performance of the plant.

ASSESSMENT CRITERIA

ASSESSMENT CRITERION 1

1. Acceptability of all operating parameters are evaluated and discussed.

ASSESSMENT CRITERION 2

2. Possible reasons for ineffective plant performance are listed and explained.

ASSESSMENT CRITERION 3

3. Recommendations that improve plant performance are given.

UNIT STANDARD ACCREDITATION AND MODERATION OPTIONS

Any person wishing to be assessed against this unit standard may apply to an assessment agency, assessor or provider institution accredited by the relevant ETQA, who may appoint a moderator to be present at the assessment.

The assessor must have knowledge and experience of air-conditioning or refrigeration.

UNIT STANDARD ESSENTIAL EMBEDDED KNOWLEDGE

The operation of single and two stage refrigeration systems
The consequences of ineffective plant performance

Critical Cross-field Outcomes (CCFO):

UNIT STANDARD CCFO IDENTIFYING

Identify and solve problems

Nature and extent of deviation from specified performance is diagnosed

Possible malfunctions are determined

UNIT STANDARD CCFO COLLECTING

Collect, analyse, organise and critically evaluate information

Critically analyse all operating parameters for correctness and possible deviation from the norms

UNIT STANDARD CCFO SCIENCE

Use science and technology effectively and critically

By understanding the processes involved

UNIT STANDARD NOTES

Assessment of this unit standard could be in the form of a written test.

QUALIFICATIONS UTILISING THIS UNIT STANDARD:

	ID	QUALIFICATION TITLE	PRE-2009 NQF LEVEL	NQF LEVEL	STATUS	END DATE	PRIMARY OR DELEGATED QA FUNCTIONARY
Core	20722	National Diploma: Air Conditioning, Refrigeration and Ventilation	Level 5	Level TBA: Pre-2009 was L5	Passed the End Date - Status was "Registered"	2004-06-13	MERSETA

PROVIDERS CURRENTLY ACCREDITED TO OFFER THIS UNIT STANDARD:

This information shows the current accreditations (i.e. those not past their accreditation end dates), and is the most complete record available to SAQA as of today. Some Primary or Delegated Quality Assurance Functionaries have a lag in their recording systems for provider accreditation, in turn leading to a lag in notifying SAQA of all the providers that they have accredited to offer qualifications and unit standards, as well as any extensions to accreditation end dates. The relevant Primary or Delegated Quality Assurance Functionary should be notified if a record appears to be missing from here.

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