constant heat flux is easy to apply experimentally

I may have 2 examples; constant heat flux could be found in solar collector tubes, constant surface temperature is related to phase change under latent heat, e.g. when you have a steam around the tubes in heat exchangers.

Thanks to Abbas J. Jubear, Ibrahim Halil Yilmaz and Elhadi I. Dekam for providing answers. Further, discussions are invited on constant heat flux and constant wall temperature.

Mostly, Constant heat flux condition, (suppling at low voltage and high current) on the surface is applied for the fluid flowing inside the tube under forced convection.

In general consideration of forced convection, there are two conditions, one is constant heat flux, where the heat is supplied by surrounding a wire around a tube, giving high voltage and low current to avoid shock and secondly for constant wall temperature, heat is supplied by surrounding a steam jacket around the tube. Constant heat flux condition is preferred and used overall

Generally in laminar flow forced convection, one come across giving heat input by constant heat flux condition or constant wall temperature condition. As constant wall temperature maintanence is difficult compared to constant heat flux, constant heat flux is preferred and adopted for heat transfer problems.

I think both conditions apply together

At one time only one cannot happen as fluid dynamics will be influenced by both factors

Thank you Mila Ilieva for your positive comment.

For all heat transfer applications in order to give a heat input to a thermal equipment, constant heat flux is preferred and adopted. This is done by surrounding a coil around the surface of where heat transfer to take place at low voltage and high current in order to avoid shock.

For giving heat input to a heat transfer apparatus, constant heat flux is the best. This is the correct way, standard one and can reasonably be adopted.

For any thermal equipment, there are two ways to give heat input, one is constant heat flux and the other constant wall temperature. Constant heat flux is got by supplying heat through a coil wound around a specimen supplying low voltage with high current whereas constant wall temperature is got by providing steam jacket around the specimen. Considering these two, it appears as constant heat flux can be applied more conveniently and more easily.

Constant heat flux condition is adopted since heat can be supplied to fluid by giving electrical heat input wound around the surface at a very low voltage and high current. As the wall temperature increases, fluid temperature also increases till both of them reached individual steady state values.

Constant heat flux is more easy and can be applied as a heat input to thermal equipment than constant wall temperature. In this, the electrical heat input can be given on the surface of the wall which goes to the fluid. It is observed that as temperature of the wall increases, the fluid temperature also increases.

Constant heat flux condition is simple and can easily be applied to give heat input to a specimen where heat is to be transferred to the fluid. The increase in heat input to the specimen increases the temperature of the fluid.

Constant heat flux condition is best suited since it can be given to the surface of the pipe by supplying the electrical energy to the pipe where the pipe itself acts as the resistance. Here the temperature of fluid as well as wall both increase along flow direction.

Owing to the existing conditions for giving heat input for forced convection, considering constant heat flux or constant wall temperature, constant heat flux would be taken for giving heat input for any thermal equipment. The reason being, this is simpler conventional, reliable and easier.

Constant heat flux is preferred since this can be applied easily to thermal equipment and the temperature can be raised to the equipment very easily by supplying through wire, low voltage and high current.

Constant heat flux condition is used since this is easier and the input be given electrically. The amount of heat input can be varied, thereby temperature can be varied and measured when this heat transfers from one fluid to other.

Constant heat flux condition is used, since this is applied at wall and the amount of heat input can be varied depending on the need.

Constant heat flux as well as constant wall temperature conditions come across in forced convection. Constant wall temperature is maintained by surrounding steam jacket out side. The temperature here be maintained at 100 degree Celsius, whereas constant heat flux is maintained by wounding wire around surface giving electrical input which can be adjusted to known temperature. Hence, constant heat flux is easier, flexible, suitable, reliable and mostly preferred.

Constant heat flux is more suited in thermal equipment since the input can be varied depending on the requirement by means of giving an electric supply through wire.

Constant heat flux and constant wall temperature conditions are used in forced convection apparatus. Compared to constant wall temperature, constant heat flux condition is more easy and the amount of input can be easily varied.

As the two conditions, constant heat flux and constant wall temperature can be applied for forced convection flow, the use of constant heat flux condition, becomes easier in the sense that the variation of heat input can be regulated nor controlled by electrical means and this will be in one's hands, hence easier.

Constant heat flux in forced convection is applied at wall. This is quite easier, since heat can be supplied by wounding electrical coil around the surface. The amount of heat to be supplied can be easily controlled and definite heat flux can be given.

In forced convection problems, there is no way but to depend on constant heat flux approach to give heat input. This approach is comparatively more standard to constant wall temperature.

Heat flux is give by Heat flow/ unit length in convection. In my view or in general constant heat flux condition is the best and easy to apply on the surface by wounding electrical coil and giving electrical heat input which can be varied depending on the need.

In constant heat flux condition both wall temperature as well as fluid temperature increases which is not so in the case of constant wall temperature condition.

Constant heat flux condition is used in all heat transfer/ thermal equipment, because of easiness and there is a way to vary heat input.

Constant heat flux condition in forced convection solves the entire problems of giving heat input. Since, heat input can be varied, reliable and easier.

In forced convection, two methods of giving heat input are considered, one is constant heat flux and the other constant wall temperature. Constant heat flux is generally adopted as it is easier and definite heat can be applied at wall which goes to fluid.

In forced convection, constant heat flux condition is applied on the surface, by wounding electrical coil. The input is given by electrical to coil by providing low voltage with high current to avoid shock and can be varied and hence there will be temperature exposed to wall and conveyed to fluid.

Out of the two conditions proposed under forced convection, constant heat flux condition is used since, giving heat input is easier, easily varied and a specific heat input be given to the thermal equipment.

Heat flux is given by total heat transfer/ length in case of tube. In forced convection, constant heat flux is more suitable and reliable for varying heat input.

Out of the conditions, constant heat flux and constant wall temperature available in giving heat input to the thermal equipment, constant heat flux is considered, as it requires a coil wound around the specimen to give heat input. The heat input can be varied and also regulated. Hence, this is more advantageous and easier.

Constant heat flux condition is applied to give heat input to thermal equipment by wounding electrical coil supplying electrically low voltage and high current and input can be varied. Whereas, constant wall temperature is supplied by surrounding steam jacket around the surface of thermal equipment.

For flow inside tubes in forced convection, constant heat flux condition is used since this is easier, heat input can be regulated and the temperature of the fluid can be increased to the required.

Out of the conditions, constant heat flux and constant wall temperature used in forced convection problems, constant heat flux condition is used in which heat input can be varied and temperature to the fluid can be regulated easily.

Constant heat flux is the most desirable condition for giving heat input electrically to thermal equipment. The input can easily be varied and raise in temperature also can easily be observed.

There are two conditions which can be applied to solve forced convection problems, one is constant heat flux and other is constant wall temperature. Constant wall temperature is got by supplying steam jacket around where the heat has to be given and therefore, temperature is maintained constant. Hence in order to have variation of temperature, heat input to equipment can be varied by electric supply and hence constant heat flux condition is generally used.

For flow inside tubes in forced convection, out of the conditions available as constant heat flux and constant wall temperature, constant heat flux condition is mostly preferred and used since this is easy as giving electric heat input. A person can easily and comfortably vary heat input according to the requirement.

. Any one can vary heat input depending on the instruments.

Taha Ahmed Abdullah, if any one can vary heat input on instruments, from my question, will you please tell me in forced convection, what are the types of inputs are there and which is preferred?

There are two ways of giving heat input to thermal equipment, one is by constant heat flux and other is by constant wall temperature. Constant heat flux condition is widely used since heat input can be given by wounding coil in the equipment plugged to electrical power supply at low voltage and high current vwhich is easier.

Constant heat flux condition is the most easiest way of giving input compared to constant wall temperature which is given electrically surrounded by a coil giving low voltage and high current. This does not give shock and the heat imput can be controlled or varied.

constant wall temperature is defined to be the case of boundary when constant temperature process occurred for example : Boiling or condensation but constant heat flux is when the boundary exposed to a constant power or heat flux like a heating power from a resistive load heating element .

in the forced convection experiments , the constant heat flux method is very convenient as the power supplied can be eaisly controlled and adjusted .