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How do you find the overall heat transfer coefficient?

How do you find the overall heat transfer coefficient?

Typical Overall Heat-Transfer Coefficients

  1. Free Convection Gas – Free Convection Gas : U = 1 – 2 W/m2K (typical window, room to outside air through glass)
  2. Free Convection Gas – Forced liquid (flowing) water : U = 5 – 15 W/m2K (typical radiator central heating)

Is higher overall heat transfer coefficient better?

Assuming the heat transfer surface and temperature difference remain unchanged, the greater the U value, the greater the heat transfer rate. In other words, this means that for a certain heat exchanger and product, a higher U value could lead to shorter batch times and increased production/revenue.

What is heat transfer coefficient in heat exchanger?

Overall heat transfer coefficient Overall heat transfer coefficient (k) is a measure of the resistance to heat flow, made up of the resistances caused by the plate material, amount of foul- ing, nature of the fluids and type of exchanger used. Overall heat transfer coefficient is expressed as W/m2 °C or kcal/h, m2 °C.

What is the heat transfer coefficient of steel?

Fluid Material in Transmission Surface Overall Heat Transmission Coefficient – U –
(W/(m2 K))
Air Mild Steel 7.9
Steam Cast Iron 11.3
Steam Mild Steel 14.2

Which one has the highest value of overall heat transfer coefficient?

Which one is having highest value of overall heat transfer coefficient? Explanation: Overall heat transfer coefficient for feed water heaters is 8500 W/m2 K while that of steam, alcohol condensers and ammonia condensers are 5000 W/m2 K, 630 W/m2 K and 1400 W/m2 K.

Does overall heat transfer coefficient change with temperature?

This in turn influences the heat transfer coefficient, despite possible identical temperature differences. The heat transfer coefficient is therefore also dependent on the direction of heat flow. In contrast to the thermal conductivity, the heat transfer coefficient is not a material constant.

Can the overall heat transfer coefficient be negative?

In addition, with traditional definition of convective heat transfer coefficient, which is based on the temperature difference of an interior surface and room air, the coefficient value can be negative.

What is Nusselt number formula?

the Nusselt number, which is NuDh = 890. the hydraulic diameter of the fuel channel is: Dh = 13,85 mm. the thermal conductivity of reactor coolant (300°C) is: kH2O = 0.545 W/m.K. the bulk temperature of reactor coolant at this axial coordinate is: Tbulk = 296°C. the linear heat rate of the fuel is: qL = 300 W/cm (FQ ≈ …

What has the highest heat transfer coefficient?

Typical heat-transfer coefficient ranges for various reactor coolants are listed in Table 4.16. It shows that sodium has the highest heat-transfer coefficients among all the proposed coolants, making it a more competitive fluid for power conversion.