Chemical Engineering - Heat Transfer - Discussion
Discussion Forum : Heat Transfer - Section 1 (Q.No. 20)
20.
The thermal efficiency of a reversible heat engine operating between two given thermal reservoirs is 0.4. The device is used either as a refrigerator or as a heat pump between the same reservoirs. Then the coefficient of performance as a refrigerator (COP)R and the co-efficient of performance as a heat pump (COP)HP are
Discussion:
12 comments Page 1 of 2.
Aksha vetal said:
9 years ago
Thermal efficiency is given by:
= (Heat transferred from higher value to lower value)/Higher value.
= (Qh - Ql)/Qh.
Thermal efficiency = 0.4 = 1- (Ql/Qh).
So,
Ql/Qh = 0.6,
Qh/Ql = 1/0.6,
(cop)R = (1 - thermal efficiency)/thermal efficiency,
(COP)R = (1- 0.4)/0.4,
(COP)R = 0.6/0.4,
= 1.5.
(COP)HP = (COP)R + 1,
= 1.5 + 1,
= 2.5.
= (Heat transferred from higher value to lower value)/Higher value.
= (Qh - Ql)/Qh.
Thermal efficiency = 0.4 = 1- (Ql/Qh).
So,
Ql/Qh = 0.6,
Qh/Ql = 1/0.6,
(cop)R = (1 - thermal efficiency)/thermal efficiency,
(COP)R = (1- 0.4)/0.4,
(COP)R = 0.6/0.4,
= 1.5.
(COP)HP = (COP)R + 1,
= 1.5 + 1,
= 2.5.
(11)
Kshema said:
1 decade ago
Kindly explain the calculation.
Khushbu chaudhary said:
1 decade ago
Thermal efficiency = 0.4 = 1-(Ql/Qh)
So, Ql/Qh=0.6
Qh/Ql=1/0.6
(COP)R=1/((Qh/Ql)-1) = 0.6/0.4
= 1.5
(COP)HP = (COP)R+1
= 1.5+1 = 2.5
So, Ql/Qh=0.6
Qh/Ql=1/0.6
(COP)R=1/((Qh/Ql)-1) = 0.6/0.4
= 1.5
(COP)HP = (COP)R+1
= 1.5+1 = 2.5
Chandana said:
1 decade ago
What is Ql and Qh?
Shan Rana said:
1 decade ago
Ql = Lower heat energy.
Qh = Higher heat energy.
Qh = Higher heat energy.
Shubham said:
1 decade ago
Thermal efficiency = 0.4 = 1-(Ql/Qh).
This term is not understand. Please again explain.
This term is not understand. Please again explain.
Ankita said:
1 decade ago
@ Shubham.
Thermal efficiency is given by:
= (Heat transferred from higher value to lower value)/Higher value.
= (Qh-Ql)/Qh.
Hence the formula.
Thermal efficiency is given by:
= (Heat transferred from higher value to lower value)/Higher value.
= (Qh-Ql)/Qh.
Hence the formula.
V G Sunjay Jeffrish said:
1 decade ago
Efficiency can also be 1-tc / th.
Where tc cold body.
Th hot body.
Where tc cold body.
Th hot body.
Sanket said:
1 decade ago
(cop)R = (1-thermal efficiency)/thermal efficiency.
(cop)Hp = 1+(cop)R.
(cop)Hp = 1+(cop)R.
Prakash Dhanaraj said:
7 years ago
How comes (cop)hp = (cop)r+1.?
Please explain.
Please explain.
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