Question

Problems - A two constant air-volume system with duct reheater similar to the one shown in the Figure is to be designed for Jeddah summer outdoor design conditions of Ta = 40°C & Txt = 24°C. Fifteen percent (15%) of the supply-air mass flow rate to each one is to be fresh air (outside air). The cooling coil for the system is to be selected such that the air will exit the coil at Td = 3°C & ° = 80 % (point 1). Assume a sensible beating of air through the fan with AT = 2C. The design thermostat setting for zone A is Ta -23°C. For the design conditions, zone A is predicted to have a sensible-heat gain of 80 kW and a lateat heat gain of 20 kW & air mikas flow rate of 9 kg/e. The design thermostat setting for zone Bis To - 26°C. For the design conditions, zone B is predicted to have a sensible heat-gain of 75 kW and a latent grin of 25 kW & air mass flow rate of 9 kg's. For the above design conditions, determine the following a) The dry bulb temperature & relative humidity for air supply to cach zone. b) The relative humidity in the zones. c) The cooling coil capacity (TR). d) The coil BPF c) The heating capacity for each heater. f) The frm motor power, assuming 0.8 3) Draw all processes on a paychrometric chart. 7 4 tur, Zone B 6 7 Cooling Coil 7E TR Fan Fresh Air Filter Do the following to satisfy Outcome 1: 1.1 Define the Problem a) Define the problem using caly essential information b) Recognize missing information and c) List necessary justified assumptions using sound principles of engineering physics, and math 12 Fomulate the Problem a) Develop a correct model for real-life problem considering all essential features using principals of engineering, science and math b) Demonstrate so conceptual or procedural trees, and c) Prove nigorous knowledge in relevant technical areas 13 Solve the Problem a) Demonstrate creative synthesis by combining knowledge and information b) Obtain meaningful solutions), and c) Reflector results Rules: 1- Only computer-generated documents for text, equations, tables & graphs should be used. No bandwritten renart will be accepted excom.io the sample calculation 2- Use EES programs to do your calculations and submit the code with your report १४

Answer 1

fan h2 = 19.4 ks Volg plot point 2 @ DBT-7°C sensible be beating so we have, Qs = m A Cp (t2-t) Qs = '9x1.0223- 80 = 9x1-02 (23-6) .t 14.29°c for Zone A NOW, we get plot point ZA @ DBT-24.29 ha = २6.25 ko legda. Now, for Zone B, Qs = 75kw as= no A Cp (T2-t) 75 = gx1.02 (26-t) It T = 17.83C Now, plot 28 @ DBT= 17.839 we gest h2B=31 W/kgda plot point 3 as line 2A-3 parallel to the SHR = 0.8 of point 4 as line 28-4 parallel to SHR = 075 IPAGE 2

we have, ros = 0.85 MA 7.65 kalech fox zone A ha= 38 kJ/rada mu 30.85 for zone B MB - 7.65 kg/sec hu = 4012 kes Iryda ) Now, we seed to plot point 5. rahat muhy so ho ms mo 7.65 [38+402) 2x 7.65 h5= 39.1 klagda Now, plot his con line 3-4 plot hoat 40°c = DBT & WBT: 246 ha=72,25 kg kJ / kgda miss If we calculate, hy then mix bangla ros = 15.3 kg/se. me=0.3x9 = 2.7 koffee so hiz= 18 kgfeed Now, Joint point 7 and point 1. mshs tincha 15:3X39 172,77825 mz 18 ht= 44 KJ lrgda PAGE 3

NOW plot 7 on 5-6 line. peoces 1-7 get Cool get cooling process a) DB7 $ $ (zone A&B) zone A At point 2A get, we get, & DBT - 14.285°C • = 49.98% Zone B + at point 2B DBT = 17.83°c = 38% b) foz E zone A D at point 3 PA = 35% fort Zone B at point 4 B = 28% > Cooling coil capacity. ce = ma (hy-hi) 718(44-17:34) = 479.88 kW bett, 1 TR = 3,5 kW ICC = 479.88 35 - 137 98 9 TPAGE

d) Coil BPF (By-Pass Facto2) - BPF -(#-to titd ty-td (5-2.5 26.5-2.5 = 0.1042 e> heating Capacity (HCA 4 HCG) HCA = MA (haa-hz) = 9 for zone A (26-25-19.4 HCA = 61.2 kW for zone B HCB - MB (628-h2) = 9 (31-19:45) HCB = 103.95kw & Power of fon Motoz (Pm) = (h2-hi) m 18 (19:45-17.34) Pma ma 0.8 Pm = 47.48 kw m ) Psychometric chart processes are are shown in Psychometric chart which is attach as below- 011 [PAYE-5

10U כשר 119 120 VUKIO. a 95 30 29 28 27 90 MALAT 80 25 75 70 ETHAY RICITY TO 65 60 20 55 go 50 20 45 Humidity Ratio, o/kg(d.a) 10% 6094 35 30 50% 6 25 40% 10 20 15 3096 10 20% 28 Zone 10% -10 -10 -5 0 5 35 40 45 50 10 15 20 25 30 Do Ruth Temperature OC Pressure 1011125 D

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