Question

Q1

a)  Company A designed a heat pump to supply heat into a library in Canada during
winter, so that the library can maintain to be at 20°C. The heat pump utilizes
12,000 L/min of Refrigerant-134a as the working fluid and absorb heat from an
industrial water stream. The water stream enters the evaporator at 50°C and exits
at 25°C. The refrigerant enters the evaporator at 10°C with 90% moisture content
and leaves at 20°C. There is no pressure drop in the evaporator and according to
Company A, the compressor consumed 2250 kW of power.

(i) Sketch a complete schematic diagram of the heat pump comprises all
components and information for the operation
(ii) Using Energy Balance in the evaporator, determine the mass flow rate of
the water stream
(iii) Calculate the rate of heating load and rate of heat supply, in kW
(iv) Find the COP of the heat pump
(v) A competitor, Company B claimed that they can come up with a more
economical design for the heat pump, consuming only 800 kW in the
compressor with the same heating load as Company A’s design. Is this claim
valid? Support your answer with proper calculation.

b)  Figure Q1(b) shows a P-v diagram consists of isentropic, polytropic, and
isothermal compression processes between the same pressure limits. Based on the
figure, distinguish the work input to the compressor for all the three processes.

P+ 2 -Isentropic (n = k) -Polytropic (1 <n<k) Isothermal (n = 1) V Figure Q1(b)

c)  Steam with the mass flow rate of 0.75 kg/s enters an adiabatic turbine steadily at
19 MPa, 600°C and 150 m/s, and leaves at 150 kPa and 350 m/s. The isentropic
efficiency of the turbine is 85%. Neglect potential energy.

(i) Determine the exit temperature of the steam, and it's quality (if saturated
mixture)
(ii) Calculate the actual power output of the turbine, in kW
(iii) Illustrate a T-s diagram with respect to saturation lines for the isentropic
process by clearly indicating all pressure, temperature, and entropy in the
correct phase state region

For the same turbine, assume the surrounding is at 25°C,
(iv) Determine the exergy per unit mass at both inlet and outlet condition
(v) Calculate the maximum (reversible) power output, in kW
(vi) Compute the second-law efficiency and the irreversibility

Answer 1

PAGE-1 *Solutions parents from the Considering the conditions with question. 4. welm Enisamel. JUUUUUUU Condes of 11 Expansion volve (2-1349 Evelostor. Compress. = 22534 1 -10c o turime Cold envirnment soc 250 with worten #Schematic Die of het pump:-) 2 20' Win=2250PW. S Eredgy Belene in Evepostos in mans + din aming 000円 toin.

PAGE 2 Oin - milherhin). -- ( my) mo Everordy 250 O 5ocit watch will att n- 25 mp. in mo (50-25) Ep. moisture content ..^= het xhfg Kalking hf. 248.55 kilky h; = ng Density of R-135 0 of R-13r o @ -20°c P = 1310 kg /m? V= 12000 lt/min +0.2mble 1310 X 0.2 = 262 kg/s in (hi hu) m Oin 1 At status = 90 Payness. fraction X=0.1 e 100 38.53 K. his 59.132 KJ/kg.

PAGE 3 Dins in Chi-hu) 256 ww = 262 (245:55 -5813) mw = 1933:43 kg/s. Moll flow rate of water streem. * Whompa in Charhi). 2250 = 262 *(ha a 254:55) h2= 253,15 kJ/kg Qout in (h2 ha) - 262 x (253.15 -59.13) dout = 508 30.04kg/ from condensar a * Copa Win COP 22.59 44 take Comp & 800 kw. wear an Cha-hi)

PAGE=4 800- 262 (62-244.55) h 2 = 247 6 kilkg Qout ń (ha-ha) +262 (254.5-59.) -Oost =-49377.1969/kg (Qout ) & (Dout ) A. so this clein is not claim: PLEASE P VOTE lot & A It is necessoly for me