Which factor is affecting the heat transfer coefficient in heat convection?
Heat transfer coefficient depends on both the thermal properties of a medium, the hydrodynamic characteristics of its flow, and the hydrodynamic and thermal boundary conditions.
What does the convective heat transfer coefficient depend on?
Accordingly, the convection heat transfer coefficient depends on (1) the fluid thermophysical properties and (2) the fluid velocity.
What is the effect of convective heat transfer coefficient on effectiveness?
The results show that (a) the greater the value of heat transfer coefficient of convection h, the smaller the efficiency fin and effectiveness fins (b) In circumstances of unsteady state, the efficiency and effectivity influenced by the value of density, specific heat, heat transfer coefficient of conduction and …
What is effect of convective heat transfer?
For a given temperature difference between hot and cold surfaces, an increase in the convection heat transfer coefficient decreases the thermal efficiency of the TEG.
How do you increase heat transfer coefficient?
To increase heat-transfer rates, the velocity through a jacket can be increased by recirculating the cooling or heating liquid. For simple jackets without baffles, heat-transfer will be mainly by natural convection and the heat-transfer coefficient will range from 200 to 400 W/m2 °C.
Does 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.
What is the difference between a local convection heat transfer coefficient and an average coefficient?
What is the difference between a local convection heat transfer coefficient and an average coefficient? What are their units? Average heat transfer coefficient is the average value over the surface. Local heat transfer coefficient is the exact heat transfer coefficient at that specific point of interest.
How does flow rate affect heat transfer?
In other words, the rate of heat transfer is directly proportional to mass flow rate. If you increase the flow rate, you will then increase the rate of heat transfer. Then, from the relationship above, increasing the mass flow rate must result in a smaller delta T because Q remains constant.
How does pressure drop affect heat transfer?
The interpretation of relation [3] is that if the pressure drop, for example, is increased four times, the heat transfer coefficient becomes 4^1/3 = 1.59 times higher than the original value, i.e. a 59% increase. Note that these proportionalities only apply to fully turbulent flow.
Why is there a pressure drop across a heat exchanger?
Pressure drop on shell side It is very common to use baffles in the shell side of shell and tube exchanger. They cause the shell side fluid to go across the tubes. This causes ‘cross flow’ conditions and promotes the overall heat transfer. For example, it is common to place a more viscous fluid on the shell side.
What is the reason for high convective heat transfer coefficient in dropwise condensation?
Dropwise condensation occurs when a vapor condenses on a surface not wetted by the condensate. For nonmetal vapors, dropwise condensation gives much higher heat transfer coefficients than those found with film condensation.
In which mode of heat transfer is the convection heat transfer coefficient usually higher?
forced convection
Why is heat transfer coefficient in forced convection greater than that in free convection?
Mechanism of Forced Convection The fluid motion enhances heat transfer (the higher the velocity the higher the heat transfer rate). The convective heat transfer coefficient h strongly depends on the fluid properties and roughness of the solid surface, and the type of the fluid flow (laminar or turbulent).