Typical Heat-Transfer Coefficients

If an error of 10% due to the simplification is accepted the maximum distance of the phase front to the heat exchanger surface smax is given in Table 22. For a typical heat transfer coefficient if water is taken as heat transfer fluid, two different cases can be observed. For the pure PCM, the maximum thickness allowed before the simplification leads to serious errors in the result is only 0.5 mm. In that case the simplification is of no practical use. If the... 

Find out about the wall construction of the cabins of large commercial airplanes, the range of ambient conditions under which they operate, typical heat transfer coefficients on the inner and outer surfaces of the wall, and the heat generation rates inside. Determine the size of the heating and air-conditioning system that will be able to maintain the cabin at 20°C at all times for an airplane capable of carrying 400 people. 

Example 1.3 A pipe made from an aluminium alloy (Am = 205W/Km) has an inner diameter of d = 22 mm and an outer diameter d2 = 25mm. Water at = 60 °C flows inside the pipe, whilst air at d2 = 25 °C flows around the outside of the pipe perpendicular to its axis. Typical heat transfer coefficients are oc = 6150W/m2K and ( 2 = 95 W/m2K. The heat flow per length of the pipe Q/L is to be calculated. 

In order to improve the heat transfer in a reactor, use can be made of gravitational forces. This concept is used in the spinning disc reactor (SDR) as developed at Newcastle University. The reaction mixture flows in a thin layer in axial direction over a rotating disc. A typical heat transfer coefficient is 10 kW/m2K. This reactor however is dedicated for liquid-liquid reactions. Especially condensation reactions can be enhanced by removing the gaseous by-products thus shifting the chemical equilibrium to the right. 

In some services (e.g., refinery fractionators), vapor approaching the chimney tray is hotter than the chimney tray liquid. Heat will be transferred from the vapor to the liquid. If the vapor is condensable, some will condense on the bottom face of the chimney tray. The net result is analogous to leakage. The author is familiar with situations where refractory was installed on the bottom face of the chimney tray. In all these cases, steps were also taken to minimize leakage, making it difficult to independently assess the effectiveness of the refractory. For multicomponent, partially condensable vapor condensing on an uninsulated bottom face of a chimney tray (e.g., in a refinery fractionator), a typical heat transfer coefficient is 15 Btu/(h ft °F) (237). 

Table 8.3-1. Typical Heat-Transfer Coefficients for Various Evaporators (B3, B4. LI, P2)... 

This is a continuation of Problem 12. Typical heat transfer coefficients given in Table 11.11 are used to predict the ratio of heat transfer resistances between boiling water and light oil. This ratio is estimated to be approximately 1 2. Estimate the individual resistance and heat transfer coefficient for both the oil and the boiling water. 

The problem with condensate backup and subcooling is the very low heat transfer coefficient (U) for subcooling vs. condensation. Typical heat transfer coefficients (Btu/hr/fb/°F) are ... 

Typical heat transfer coefficient ranges for various reactor coolants are listed in Table A2.7. It shows that Na has the highest heat transfer coefficient among all the proposed coolants, making it a more competitive fluid for power conversion. 

A typical heat transfer coefficient for the system demineralized water-raw water is within the range 300-500 Btu/ft h °F. Assume the overall heat transfer coefficient is 400 Btu/fC h °F... 

A major attractiveness of fluidized beds for many applications is the high heat transfer rate that may be attained between the emulsion phase and the wall typical heat transfer coefficients that have been reported in the literature range from about 60 to 500 Btu/hr ft °F (8 x 10 -6.5 x 10" cal/cm sec °C ) and similar values have also been found for the heat transfer coefficients between the emulsion and heating or cooling elements (coils, etc.) immersed in the bed. 

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