Which fluid properties are important in heat transfer?

The ability of a fluid to transfer heat across an interface depends on the fluid properties of viscosity, thermal conductivity, specific heat and density. For good heat transferability, the viscosity should be low, while the other three properties should be high.

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 is the effect of Reynolds number on heat transfer coefficient?

The convective heat transfer coefficient increases with the increase of Reynolds number in an inclined tube. In an inclined tube, the surface friction coefficient of the length tube decreases when the Reynolds number is increased.

What is the effect of convection heat transfer coefficient h’on fin effectiveness?

The higher value of h causes the smaller efficiency and effectivity of the fin. Sahin and Demir, 2008 found that heat transfer coefficient (h) affect to the fin’s performance. This is because the temperature distribution generated on the fin has a closer temperature with the fluid around the fin [5].

How is heat transferred in a fluid?

When the object is a fluid, heat can be transferred from the fluid to another object by flow of the fluid on the surface of the object. This type of heat transfer is called convection. Convection can transfer larger amounts of heat than conduction.

How the type of fluid affects the heat transfer coefficient?

Heat transfer coeficiente depends on the kind of fluid involved. Each fluid has its own thermal properties, which can be found in published tables and books. Thermal conductivity of a given material that receives thermal energy by means of some fluid affects the heat transfer process, too.

What factors affect convection heat transfer?

Convection heat transfer is treated empirically because of the factors that affect the stagnant film thickness:

• Fluid velocity.
• Fluid viscosity.
• Heat flux.
• Surface roughness.
• Type of flow (single-phase/two-phase)

How does flow rate affect heat transfer coefficient?

The heat transfer coefficient decreases by ˜10\% with a threefold increase in the mass flow rate under these conditions, based on the commonly used Dittus-Boelter correlation for estimation of the heat transfer coefficient. Doubling the mass flow rate will result in a 92\% increase in the heat transfer coefficient.

How does an increase in the Reynolds number effect heat transfer in finned heat exchangers?

At higher Reynolds numbers, the effect of flow unsteadiness is to increase overall heat transfer and associated frictional loss.

What is effect of thermal conductivity on fin effectiveness?

Results show that the PCHE fin effectiveness is enhanced by the choices of high fin thermal conductivity, decreasing the ratio of the fin thickness to the radius of the channels, or under conditions for which the convective coefficient is small.

Why Aluminium is used as a fin material?

Good corrosion resistance, formability and high thermal conductivity make aluminium an ideal material for the construction of these heat exchangers.

What is the convective heat transfer coefficient of fluid?

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). Fig. 1: Forced convection. It is assumed that the velocity of the fluid is zero at the wall, this assumption is called no‐ slip condition.

What is the rate of heat transfer from solid to fluid?

The rate of heat transfer between a solid surface and a fluid per unit surface area per unit temperature difference. The convective heat transfer coefficient is dependent upon the physical properties of the fluid and the physical situation. The convective heat transfer coefficient is not a property of the fluid.

Why is thermal conduction the limiting case of convection?

Therefore, thermal conduction in a fluid can be viewed as the limiting case of convection, corresponding to the case of quiescent fluid. Some experts do not consider convection to be a fundamental mechanism of heat transfer since it is essentially heat conduction in the presence of fluid motion.

What are the effects of free convection on heat transfer?

Depending on the situation, free convection can make a considerable contribution to the total heat transfer. If a fluid flows along a wall, this has an effect on the flow velocity. Due to the frictional forces (described by the viscosity) between wall and fluid and within the fluid, the flow velocity of the fluid is disturbed.