INSTRUCTION: This section consists of SIX (6) structure questions. Answer FOUR (4) questions only.

Size: px

Start display at page:

Download "INSTRUCTION: This section consists of SIX (6) structure questions. Answer FOUR (4) questions only."

Gabriel Barton
5 years ago
Views:

1 INSTRUCTION: This section consists of SIX (6) structure questions. Answer FOUR (4) questions only. ARAHAN: Bahagian ini mengandungi ENAM (6) soalan struktur. Jawab EMPAT (4) soalan sahaja. QUESTION 1 SOALAN 1 a) A refrigeration system employing R-134a is operating on : Sebuah sistem penyejukan beroperasi dengan menggunakan R-134a : Power : 1 kw Kuasa : 1 kw Suction temperature : 5⁰C Suhu sedutan : 5⁰C Discharge temperature : 63⁰C Suhu discas : 63⁰C Condensing temperature : 50⁰C Suhu pemeluwapan : 50⁰C Evaporating temperature : -5⁰C Suhu penyejatan : -5⁰C Superheat temperature : 10⁰C Suhu haba lampau : 10⁰C Sub cooled temperature : 10⁰C Suhu sejuk lampau : 10⁰C Liquid temperature at TXV inlet : 40⁰C Suhu cecair memasuki TXV masukkan : 40⁰C Calculate: Kirakan: i. Compression ratio Nisbah mampatan 2 SULIT

2 ii. Refrigeration effect Kesan penyejukan iii. Mass flow rate of refrigerant ( g / s ) Kadar alir bahan pendingin iv. Heat of compression Haba mampatan v. Percentage of flash gas Peratus haba lampau vi. Coefficient of performance Angkali kecekapan/kelakunan sistem CLO2 b) Plot the refrigeration cycle of the system in question ONE (1) (a) on the R-134a Mollier chart provided. Plotkan kitaran penyejukan bagi sistem di dalam soalan SATU (1) (a) pada carta Mollier R-134a yang disediakan. (4 marks) (4 markah) c) Calculate the overall heat transfer coefficient for a condenser with a capacity of Qc = 800W, surface area, A = 8 m 2 and a temperature difference between the condensing refrigerant and the air of TD = 12 C. Kirakan kadar pemindahan haba pada sebuah pemeluwap dengan kapasiti Qc = 800W, kawasan permukaan, A = 8 m 2 dan perbezaan suhu di antara pemeluwapan bahan pendingin dan udara = 12 C. (3 marks) (3 markah) 3 SULIT

3 d) Calculate the compressor displacement (l/sec) of FOUR (4) cylinder compressor running at the speed of 1200rpm. The diameter of each cylinder is 5cm and the length of stroke is 4cm. Kirakan jumlah anjakan omboh pemampat (l/sec) yang mempunyai EMPAT (4) selinder bergerak pada kelajuan 1200rpm.Garis pusat setiap selinder adalah 5cm dan panjang lejang adalah 4cm. (3 marks) (3 markah) QUESTION 2 SOALAN 2 (a) Define the following psychometric terms: Terangkan istilah psikometrik berikut: i. Dew point temperature Suhu titik embun ii. Humidity ratio Nisbah kelembapan (5 marks) (5 markah) (b) Two air streams are mixed steadily and adiabatically. The first stream enters at 32 C and 40% relative humidity at the rate of 20 m/min, while the second stream enters at 12 C and 90% relative humidity at the rate of 25 m/min. Assuming that the mixing process occurs at the pressure of 1 atm. Determine the specific humidity, the relative humidity, the dry-bulb temperature, and the volume flow rate of the mixture. Dua aliran udara dicampurkan dengan mantap dan adiabatik. Aliran pertama masuk pada 32 C dan 40% kelembapan pada kadar 20 m / min, manakala aliran kedua masuk pada 12 C dan 90% kelembapan pada kadar 25 m / min. Dengan mengandaikan bahawa proses pencampuran berlaku pada tekanan 1 atm. Tentukan kelembapan tertentu, kelembapan relatif, suhu bebuli kering, dan kadar aliran isipadu campuran. 4 SULIT

4 (20 marks) (20 markah) QUESTION 3 SOALAN 3 CLO2 a) Sketch the Carnot cycle which consist of compressor, boiler, turbine and condenser. Then, convert the cycle to T-s diagram. Lakarkan kitar Carnot yang mengandungi pemampat, dandang, turbin dan pemeluwap. Kemudian, pindahkannya kepada rajah T - S. (8 marks) (8 markah) CLO2 C2 b) Based on question THREE (3) (a) above, explain briefly on Carnot cycle process. Berdasarkan soalan TIGA (3) (a) di atas, terangkan secara ringkas tentang proses kitar Carnot. (8 marks) (8 markah) CLO2 c) A machine working on reverse carnot cycle operates between 35 0 C and C. Determine the COP if the machine is: Sebuah mesin yang beroperasi secara kitaran karnot terbalik di antara 35 0 C dan C. Kirakan COP jika mesin ini sebagai: i. A refrigerator Peti sejuk 5 SULIT

5 ii. iii. A heat pump Pam haba A heat engine Enjin haba (9 marks) (9 markah) QUESTION 4 SOALAN 4 CLO 2 CLO 2 CLO 2 C2 (a) Define Specific Heat. Takrifkan maksud Haba Tentu. (b) State the difference between heat and temperature. Nyatakan perbezaan diantara haba dan suhu. (c) List and explain THREE (3) methods of heat transfer. Senarai dan terangkan TIGA (3) kaedah pemindahan haba. (4 marks) (4 markah) (4 marks) (4 markah) (9 marks) (9 markah) CLO 2 (d) A 24.57gram sample of metal at 75.2ºC was placed in gram water at 22.6ºC. The final temperature of the water and metal were 34.6ºC. If there is no heat lost to the surrounding, calculate the specific heat of the metal. Besi seberat 24.57gram pada suhu 75.2 ºC telah diletakkan ke dalam gram air yang bersuhu 22.6 ºC. Suhu akhir besi dan air adalah 34.6 ºC. Jika tidak ada kehilangan haba yang berlaku disekeliling, kirakan haba tentu bagi besi tersebut. (8 marks) (8 markah) 6 SULIT

6 QUESTION 5 SOALAN 5 CLO3 a) Define the function of Heat Exchanger. Tentukan fungsi alat penukar haba. (3 marks) (3 markah) CLO3 b) List FOUR (4) types of Heat Exchanger used in the air conditioning and refrigeration system. Senaraikan EMPAT (4) jenis alat penukar haba yang digunakan di dalam sistem penyamanan udara dan penyejukan. (4 marks) (4 markah) CLO3 C2 c) One common characteristic that can be used to categorize the heat exchanger is the direction flow of the two relative fluids to each other. Draw and explain the counter flow method of the heat exchanger. Salah satu ciri biasa yang boleh digunakan untuk mengkategorikan alat penukar haba adalah arah aliran dua bendalir yang relatife kepada satu sama lain. Lukis dan terangkan kaedah aliran berlawanan alat penukar haba tersebut. (6 marks) (6 markah) CLO3 d) Figure 1 shows the parallel flow method of the heat exchanger. From this condition, calculate the rate of heat transfer in a heat exchanger if the cross sectional heat transfer area is 75 ft 2. Assume that overall heat transfer coefficient is 70 BTU/hr ft 2 ⁰F. Rajah 1 menunjukkan kaedah aliran selari alat penukar haba. Dari keadaan ini, kirakan kadar pemindahan haba di dalam penukar haba jika kawasan pemindahan haba keratan rentas ialah 75 ka 2. Anggapkan bahawa Pekali pemindahan haba keseluruhan ialah 70 BTU / jam ka 2 ⁰F. 7 SULIT

7 Figure 1 (12 marks) (12 markah) QUESTION 6 SOALAN 6 CLO 3 CLO 3 (a) Define Low Temperature System. Takrifkan Sistem Suhu Rendah. (b) (i) Sketch the operation of the Cascade Staging System. Lakarkan prinsip kendalian bagi sistem mampatan berperingkat (3 marks) (3 markah) (6 marks) (6 markah) (ii) Explain the operation principle of cascade staging system. Terangkan prinsip kendalian bagi sistem mampatan berperinkat (6 marks) (6 markah) 8 SULIT

8 CLO 3 C2 (c) (i) Sketch and label a hot-gas defrosting system. Lakar dan labelkan gambarajah sistem hot-gas defrosting. (5 marks) (5 markah) (ii) Explain briefly the operation of the hot-gas defrosting system. Terangkan secara ringkas operasi sistem hot-gas defrosting. (5 marks) (5 markah) SOALAN TAMAT 9 SULIT

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

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.