INSTRUCTION: This paper consists of SIX [6] structured questions. Answer any FOUR [4] questions.

Transcription

1 JU20:AIR CONDITIONING AND REFRIGERATION TECHNOLOGY INSTRUCTION: This paper consists of SIX [6] structured questions. Answer any FOUR [4] questions. ARAHAN: Kertas ini mengandungi ENAM [6] soalan struktur. Jawab mana-mana EMPAT [4] soalan. QUESTION SOALAN (a) Define Berikan definasi i. Absolute pressure i. Tekanan mutlak ii. Gauge pressure ii. Tekanan tolok iii. Vacuum pressure. iii. Tekanan vakum C3 iv. A pressure gauge attached to a pipe indicates a reading of 30 psi. Calculate the absolute pressure in the pipe. Given: P [atm] = 4.7 psi iv. Tolok tekanan yang dipasang pada paip menunjukkan bacaan tekanan sebanyak 30 psi. Apakah tekanan mutlak didalam paip tersebut. Diberi: P [atm] = 4.7 psi 2

2 JU20:AIR CONDITIONING AND REFRIGERATION TECHNOLOGY C3 (b) i. A room is cooled from 40 C to a required condition with temperature difference of 20 K. Calculate the new temperature of the room in F. i. Sebuah bilik disejukkan daripada suhu 40 C kepada suhu yang dikehendaki dengan perbezaan sebanyak 20K. Kirakan suhu baru bilik tersebut dalam F. (c) Determine the value of corresponding pressure of a fluid in the space provided. Tentukan nilai tekanan bendalir didalam ruang yang disediakan. Pressure atm mmhg kpa psi [2 marks] QUESTION 2 SOALAN 2 (a) List the basic component of air conditioning and refrigeration system. Senaraikan komponen asas di dalam sistem penyaman udara dan penyejubekuan. (b) Sketch the basic cycle of refrigeration for a split unit air conditioning system. Lakarkan kitaran asas penyejukan untuk penyaman udara unit pisah. [7 marks] [7markah] 3

3 JU20:AIR CONDITIONING AND REFRIGERATION TECHNOLOGY (c) List FOUR [4] examples of water cooled evaporator. Senaraikan EMPAT [4] contoh penyejat sejuk air. (d) Describe FIVE [5] differences between split unit air conditioning and window type air conditioning. Berikan LIMA [5] perbezaan diantara penghawa dingin unit pisah dan unit tingkap [0 marks] [0 markah] QUESTION 3 SOALAN 3 (a) i. Define a centrifugal compressor. ii. Berikan definasi pemampat empar. ii.describe the function of a condenser ii. Terangkan prinsip kerja pemeluwap. iii. Explain TWO [2] advantages and TWO [2] disadvantages of: iii.terangkan DUA [2] kelebihan DUA [2] keburukan: a. An open type compressor a. Pemampat jenis terbuka [4marks] 4

4 JU20:AIR CONDITIONING AND REFRIGERATION TECHNOLOGY b. A semi hermetic type compressor b. Pemampat separa tertutup. c. A hermetic type compressor. c. Pemampat jenis tertutup (b) Explain with the aid of a sketch the function of internal equalizing thermostatic expansion valve. Jelaskan dengan bantuan lakaran fungsi injap termostatik jenis pengembangan dalam. [7 marks] [7markah] QUESTION 4 SOALAN 4 a. i. Explain the function of a condenser. i.terangkan fungsi pemeluwap [3markah] ii. List TWO [2] types of condenser according to its cooling method. ii. Berikan DUA [2] jenis pemeluwap mengikut kaedah penyingkiran haba. 5

5 JU20:AIR CONDITIONING AND REFRIGERATION TECHNOLOGY b. Identify the type of condenser used in domestic refrigerator. Explain with a sketch. Apakah jenis pemeluwap yang digunakan di dalam peti sejuk domestik? Jelaskan beserta lakaran. [5 marks] [5markah] c. Explain with the aid of a sketch the difference between double tube condenser and shell and tube condenser. Terangkan dengan bantuan lakaran perbezaan diantara double tube type condenser dan shell and tube type condenser. [5 marks] [5markah] QUESTION 5 SOALAN 5 a. i. Define primary and secondary refrigerant. i.berikan maksud bahan penyejuk pertama dan kedua. ii. List TWO [2] examples of secondary refrigerant. ii.berikan DUA [2] contoh bahan penyejuk kedua b. List THREE [3] chemicals properties of a refrigerant. Berikan TIGA [3] sifat kimia bahan penyejuk [3 markah] 6

6 JU20:AIR CONDITIONING AND REFRIGERATION TECHNOLOGY c. i. Explain why boiling temperature of refrigerant at atmospheric pressure should be low. i.jelaskan mengapa suhu didih bahan penyejuk sepatutnya rendah pada tekanan atmosfera. [5 marks] [5markah] ii. Explain whether ammonia can be used as refrigerant in a copper condenser. ii.terangkan samada bahan penyejuk ammonia boleh digunakan pada penyejat yang diperbuat daripada tembaga.. [5 marks] [5 markah] d. i. Explain azeotropes refrigerant. i. Terangkan maksud bahan penyejuk azeotropes. ii. List TWO [2] examples of azeotropes refrigerant. ii. Senaraikan DUA (2) contoh bahan penyejuk azeotropes. QUESTION 6 SOALAN 6 a. Identify the metering device used in domestic refrigerator. Kenalpasti apakah jenis peranti pemeteran yang digunakan pada peti sejuk domestic. [2markah] 7

7 JU20:AIR CONDITIONING AND REFRIGERATION TECHNOLOGY b. Differentiate between mechanical compression cooling system and absorption cooling system. Bezakan antara sistem penyejukan mampatan mekanikal dan sistem penyejukan penyerapan. [5marks] [5markah] c. List FOUR [4] types of air conditioner. Senaraikan EMPAT [4] jenis penghawa dingin d. Sketch the basic cycle of a split air conditioning unit and a window unit. Lakarkan kitaran asas penyaman udara jenis pisah dan jenis tingkap. [4 marks] [4 markah] SOALAN TAMAT 8