Question

The black grille on the back of a refrigerator has a surface temperature of 35°With a total surface area of 1m2. Heat transfer to the room air at 20°C takes place with an average convective heat transfer coefficient of 15 W/m2 K. How much energy can be transferred to the room during 15 minutes of operation?

Answer 1

E=202.5 KJ

Step-by-step explanation:

Given that

T₁= 35°C

T₂=20°C

h=15 W/m² K

A= 1 m²

t=15 min

Energy transfer

Q= h A ΔT

Now by putting the values

Q= h A ΔT

Q= 15 x 1 x (35-20)

Q= 15 x 15 = 225 W

We know that W= J/s

So energy transfer in time 15 min

E= Q . t

E= 225 x 15 x 60 = 202500 J

E=202.5 KJ