In determining the heat transfer characteristics of a heat exchanger, it is important to have a clear picture of the physical exchanger prior to calculations. For example, in a pipe heat exchanger, it is common to determine the UA for a unit length of pipe. An exchanger can then be sized to meet the heat transfer requirements. Consider a heat exchanger of stainless steel tubes with the cross section shown in Figure 4. Each tube is 1-in. OD with the following dimensions:

D1 = inside diameter = 0.782 in. (0.0199 m) D0 = outside diameter = 1.000 in. (0.0254 m) xw = wall thickness = 0.109 in. (0.00277)

The heat transfer coefficients are inside: h{ = 120 Btu/(h)(ft2)(°F) or 681 W/m2 • K inside fouling: = 660 Btu/(h)(ft2)(°F) or 3748 W/m2 • K outside fouling: h„s = 1000 Btu/(h)(ft2)(°F) or 5678 W/m2 • K outside: h0 = 1500 Btu/(h)(ft2)(°F) or 8517 W/m2 • K

and the conductivity of the stainless steel tube is k = 9.4 (Btu)(ft)/(h)(ft2)(°F) or 16.3 W-m/m2-K

Determine UA for the tubes in this heat exchanger. Basis:

Homemade Pet Food Secrets

Homemade Pet Food Secrets

It is a well known fact that homemade food is always a healthier option for pets when compared to the market packed food. The increasing hazards to the health of the pets have made pet owners stick to containment of commercial pet food. The basic fundamentals of health for human beings are applicable for pets also.

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