What does the convective heat transfer coefficient depends on?

Accordingly, the convection heat transfer coefficient depends on (1) the fluid thermophysical properties and (2) the fluid velocity. These factors should be considered in the analysis and design of energy geostructures.

Why the convection heat transfer coefficient at a surface reduces in the fluid flow direction for the flow over a flat plate in laminar flow?

If the boundary layer is laminar, the effective thermal conductivity is equal to the fluid molecular thermal conductivity. For this situation, the heat transfer coefficient (i.e. the inverse of the resistance) is inversely proportianal to the thickness of the boundary layer.

How does laminar flow affect heat transfer?

Defined as fluid gliding through a channel in smooth layers, where the innermost layer flows at a higher rate than the outermost. Laminar flow develops an insulating blanket around the channel wall and restricts heat transfer. Full size pipes and hoses are recommended to avoid restricting the flow.

What are the factors affecting overall heat transfer coefficient?

The factors affecting overall heat transfer coefficient are :

• Physiochemical properties of fluids ( both cold and hot ) such a viscosity , density, specific heat, thermal conductivity.
• Geometry of the exchanger ( equivalent length and heat exchanging area )
• Velocity of flowing fluids.

What affects convection coefficient?

Convective heat transfer coefficients – hc – depends on type of media, if its gas or liquid, and flow properties such as velocity, viscosity and other flow and temperature dependent properties.

How does convection contribute to the heat transfer?

Convection is heat transfer by mass motion of a fluid such as air or water when the heated fluid is caused to move away from the source of heat, carrying energy with it. Convection above a hot surface occurs because hot air expands, becomes less dense, and rises (see Ideal Gas Law).

Why is heat transfer coefficient in forced convection greater than that in free convection?

Why heat transfer coefficient for natural convection is much lesser than that of forced convection? (NOV-DEC 13] The convection heat transfer coefficient will usually be higher in forced convection and lower in free convection since heat transfer coefficient depends on the fluid velocity, and free convection involves …

Why heat transfer coefficient is higher in turbulent flow?

Under turbulent flow conditions, the increase in heat transfer rate is more significant than that under laminar flow conditions. This is due to the increase in the Reynolds number of the flowing fluid in turbulent flow. The turbulent effects become a dominant factor over secondary flow at higher Reynolds number.

What is the convection heat transfer coefficient?

The convective heat transfer coefficient, h, can be defined as: The rate of heat transfer between a solid surface and a fluid per unit surface area per unit temperature difference.

Where does convection heat transfer occur?

Convection currents transfer thermal energy through many fluids, not just hot water in a pot. For example, convection currents transfer thermal energy through molten rock below Earth’s surface, through water in the oceans, and through air in the atmosphere.

What is the convective heat transfer coefficient of laminar flow?

Typically, the convective heat transfer coefficient for laminar flow is relatively low compared to the convective heat transfer coefficient for turbulent flow. This is due to turbulent flow having a thinner stagnant fluid film layer on the heat transfer surface.

How does the convective heat transfer coefficient change with altitude?

As a result, the convective heat transfer coefficient significantly increases and therefore at higher elevations, the temperature difference (T Zr,1 – T bulk) significantly decreases. Fundamentals of Heat and Mass Transfer, 7th Edition.

What is the convection heat transfer coefficient of seepage flow?

In the analysis of internal and external flows, the convection heat transfer coefficient, hc, is typically used to express with the relevant temperature variation, ΔT, the heat flux density. In the analysis of seepage flows, the separate terms ρfcpfˉvrf are used to equivalently express the convection heat transfer coefficient.

How to determine convection heat transfer coefficient from collector glazing?

The determination of heat transfer by convection from the collector glazing to ambient is a quite difficult task. The convection heat transfer coefficient hcc−a is influenced by collector dimensions, its slope, airflow yaw angle, turbulence intensity, and the ratio of free to forced convection.