Reason fo I.EE regulations in electrical installations
1 answer:
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Given:
Temperature of water, =
=273 +(-6) =267 K
Temperature surrounding refrigerator, =
=273 + 21 =294 K
Specific heat given for water, = 4.19 KJ/kg/K
Specific heat given for ice, = 2.1 KJ/kg/K
Latent heat of fusion, = 335KJ/kg
Solution:
Coefficient of Performance (COP) for refrigerator is given by:
Max =
= = 9.89
Coefficient of Performance (COP) for heat pump is given by:
Max =
= 10.89
Answer:
The net energy transfer from the student's body during the 20-min ride to school is 139.164 BTU.
Explanation:
From Heat Transfer we determine that heat transfer rate due to electromagnetic radiation (), measured in BTU per hour, is represented by this formula:
(1)
Where:
- Emissivity, dimensionless.
- Surface area of the student, measured in square feet.
- Stefan-Boltzmann constant, measured in BTU per hour-square feet-quartic Rankine.
- Temperature of the student, measured in Rankine.
- Temperature of the bus, measured in Rankine.
If we know that ,
,
,
and
, then the heat transfer rate due to electromagnetic radiation is:
Under the consideration of steady heat transfer we find that the net energy transfer from the student's body during the 20 min-ride to school is:
(2)
Where is the heat transfer time, measured in hours.
If we know that and
, then the net energy transfer is:
The net energy transfer from the student's body during the 20-min ride to school is 139.164 BTU.