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Flashcards in Units Deck (9)
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1

What do W and Ẇ indicate

W is total work done by the system

Ẇ is work done per unit of mass

2

What do Q, q and  Q̇ indicate

Q indicates total quantity of heat (joules)

q (indicates rate of heat flow) power 

Q̇ indicates rate of work flow per unit of mass

3

4

What is the units of entropy

kj/kg

5

What in the steam tables what is Hf Hg and Hfg

Hf is the enthalpy of a saturated fluid at a specific temperature. Hg is the Enthalpy of a saturated vapour at a specific temperature. Hfg is the difference between the two which is the specific enthalpy change of vapourisation. Hf is always m higher than Hg because most of the energy in steam is latent heat not sensible heat. 

 

6

How is convective heat transfer calculated

Q = hA(delta T)

 

h =convection heat transfer coefficient, W/m2 °C

A =heat transfer surface area, m2

Ts =temperature of the surface, °C

T (infinity)=temperature of the fluid sufficiently far from the surface, °C

7

What is h with regards to convective heat transfer

It is the convective heat transfer coefficient

8

What is k with regards to heat transfer

thermal conductivity of the material W/m2

9