BME-043 I

Diploma in Electrical and Mechanical Engineering Term-End Examination December, 2009 BME-043 : RAC/UTILIZATION

Maximum Marks : 70

Time : 2 hours

Note : All questions are compulsory. Use of calculator is allowed. Psychometric chart is provided.

1.

Choose the correct answer.

14x1=14

(a) The main difference between a refrigerating machine and a heat pump is in their. Operating pressure. Operating temperature. Net volume. None of the above. (b) Which one is the designation of R 718 ? (i)

Water

(ii) Ammonia

(iii) Carbon Dioxide (iv) Methane BME-043

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P.T.O.

In counter flow heat exchanger, the direction of,flow of hot and cold fluid is : (i)

Same

(iii) At 90°C

(ii) Opposite (iv) None of the above

Density of a good refrigerant should be : As small as possible As large as possible Medium Nothing can be said Viscosity of refrigerant should be : (i)

low

(iii) medium

(ii) high (iv) nothing can be said

Newton's law of cooling gives heat transfer by : Radiation Convection Conduction Radiation and Conduction

(g) Air conditioning means control of temperature and humidity temperature alone humidity temperature, humidity, cleanliness and air motion. BME-043

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(h)

(i)



(j)

(k)

W m -1 K -1 is the unit of : Thermal conductivity Thermal resistance Heat transfer coefficient None of the above As per Fan law's, which is the correct one ? (ii) Q a N3 (i) Q a N2 (iv) Q a N4 QaN The factors that affect the solar heat gain are : Location Time of day Time of year All of the above Which of the following type of compressor is used in room air conditioner. Axial compressor Centrifugal compressor Screw compressor

(1)

BME-043

Hermitic compressor Wilson plot technique is used in relation to : Heat engine Centrifugal fan Heat exchanger None of the above 3

What should be the optimum inside humidity for comfort summer air conditioning ? (i) 45% - 55% (ii) 55% - 65% (iv) 25% - 35% (iii) 35% - 45% A vertical line directing upward in a psychrometric chart shows. Cooling Heating Humidifying Dehumidifying 2. Answer any two of the following : 7 + 7=14 What do you mean by a refrigerant ? What are the desirable characteristics of a refrigerant ? What are the various components of the vapour compression system ? Explain their functions. (c) What do you mean by air-conditioning ? What are its various applications ? 3. Answer any two of the following : 7 + 7=14 (a) Explain the terms - Dry bulb temperature, wet bulb temperature, specific humidity, Enthalpy. BME-043



4

P.T.O.

Describe in brief, designing of an air - conditioning system. What are the different types of air filters ? Describe any two filters. 4. Answer any two of the following :



7 + 7=14

List out the sources of internal heat gain and system heat gains in air conditioning applications. What is room sensible heat factor ? How is the RSHF line drawn on psychrometric chart ? (c) What are the inside design conditions of air conditioning ? Explain any one of them. 5. Answer any two of the following :

7 + 7=14

What are the various types of the insulation materials ? List any two advantages and disadvantages. What is meant by condensing unit ? How the performance characteristics of a condensing unit are determined ? (c) What is meant by temperature gradient ? Derive fourier's equation for conduction heat transfer. -o0oBME-043

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