(1)(a) State three general safety precautions to be observed in a
refrigeration and air- conditioning workshop.
(b) List the three states of matter.
(c)(i) sketch a thermometer.
(ii) Label three parts of the sketch made in (1)(c)(i).
Most of the candidates who attempted this question performed excellently well in parts (a) and (b). The required sketch for part (c) is given below:
The sketch above shows a refrigeration cycle.
- Identify the type of refrigeration system.
- Identify the parts labelled P, Q, R, S and T.
- State the functions of the parts labelled P, Q, S and T.
This question was very difficult for the candidates as they could not provide the required responses to the various parts of the question. The required responses are:
- vapour compression system.
- P is Compressor
Q is Condenser
R is Drier
S is Control valve/metering device
T is Evaporator.
- P is to suck in refrigerant, compresses the refrigerant and discharge the refrigerant.
Q is to reject the heat from the refrigerant and change the state of the refrigerant from vapour to liquid.
S is to regulates and meters the amount of refrigerant flowing into the evaporator.
T is to absorb heat from the products to be cooled and change the state of the refrigerant from liquid to vapour.
(a) List the three types of compressor that are commonly used in refrigeration and air-conditioning industry.
(b) Sketch a reciprocating compressor and label five of its parts.
(c) Explain the function of a condenser.
(a) Define an insulator.
(b) State three properties of an insulating materials
(c) A cold room has its walls measuring 10 m by 4 m. If the conditional
temperature is 5OC and the outer temperature is 28OC, calculate the total heat transmitted through the wall. (take U – factor to be 0.93W/m2K).
Candidates performed well in parts (a) and (b) of the question. The required response to part (c) of the question is given below:
Area = L x B
= 10 x 4
Temperature difference (TD) = 28OC – 5 OC = 23 OC
U = O.93 W/m2K
Q = A x U x TD = 40 m2 x O.93W/ m2K x 23 OC
(a) List five sources of finance available to a refrigeration and air –
(b) Explain the following business concept:
(ii) sole proprietorship.
(c) Define the following terms:
(i) working capital;
(ii) fixed capital.
This question did not pose any problem to the candidates that attempted it.
The paper compared favourably with those of previous years in standard, the skills tested and the coverage of the prescribed examination syllabus. The questions were straight forward and clearly itemized to ease comprehension. The rubrics were clear and the marking scheme was flexible and exhaustive.
Candidates’ performance was lower than that of the previous year. A total of 952,983 candidates sat for the paper with a raw mean score of 27 and a standard deviation of 10.72 as against a raw mean score of 33 and a standard deviation of 10.39 recorded in the May/June 2013 WASSCE which had candidates’ population of 1,305,194.
A SUMMARY OF CANDIDATES’ WEAKNESSES
Candidates’ weaknesses were shown in their inability to compute correctly and sketch components.
SUGGESTED REMEDIES FOR OVERCOMING WEAKNESSES
The following were the suggestion made if the weaknesses are to be remedied:
– teachers should teach the students properly and encourage them to sketch the components in air-conditioning and refrigeration;
– teachers should give students assignments that would help to improve students computational skills;
– qualified technical personnel should be employed to teach the students workshop practices;
– seminars and workshops should be organize for the teachers, to update their knowledge.
Candidates responded to most of the questions by giving the relevant responses required of them and supporting their points with examples