# Heat exchanger Q?

#### OMANII93

Hi,
I need someone to help me with this question. I tried to find the answer for two weeks I could not finde it. Anyone with the required experience can help!! I will be so grateful.

Question:

A shell-and-tube heat exchanger is to act as a condenser: saturated ethyl alcohol (ethanol) vapour at pressure of 1 atm is to be condensed on the shell side and cooling water will be used in the tubes. U-tubes will be used (giving two passes on the tube-side). They will be steel, with a total length (end-to-end of a U-tube) of 6m, 15 mm inside diameter and 17.5 mm outside diameter. Thermal conductivity of steel can be taken as 50 W/m/K.

It is required to condense a maximum vapour flow of 5000 kg/h with no sub-cooling of the condensate. Cooling water is available with a maximum summer temperature of 25°C and with the temperature-rise (DT) limited to 30°C. A search of the literature shows that a heat transfer coefficient of around 5000 W/m2/K can be expected on the shell side for condensing ethanol. Fouling factors on the inner and outer tube surfaces may be assumed to be 0.0001 m2×K/W and 0.0002 m2×K/W respectively.

Determine the number of tubes required, the overall heat transfer coefficient and the effectiveness of the heat exchanger.

Fluid properties may be evaluated at mean fluid temperature. Other assumptions made must be fully justified.

#### leesajohnson

Heat transfer coefficient

Heat transfer coefficient
h = \frac{q}{\Delta T}
Where:
q: amount of heat transferred (heat flux), W/m2 i.e., thermal power per unit area, q = d{\display style {\dot {Q}}}/dA
h: heat transfer coefficient, W/(m2•K)
ΔT: difference in temperature between the solid surface and surrounding fluid area, K.
Reference-http://www.brighthubengineering.com/hvac/59900-fundamentals-of-heat-exchanger-theory-and-design/

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