# Does overall heat transfer coefficient change with temperature?

## Does overall heat transfer coefficient change with temperature?

Factors influencing the heat transfer coefficient However, the temperature distribution in the fluid is different. 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.

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 the value of overall heat transfer coefficient for steam condenser?

Explanation: Overall heat transfer coefficient for air condensers is 780 W/m2 K while that of steam condensers, air to low viscosity liquids and feed water heaters are 5000 W/m2 K, 600 W/m2 K and 8500 W/m2 K.

Does heat transfer coefficient change with flow rate?

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.

#### What affects the heat transfer coefficient?

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. …

How does the effectiveness change if the overall heat transfer coefficient is increased?

How does the effectiveness change if the overall heat transfer coefficient is increased? Issues with increasing the overall heat transfer coefficient are that it increased the velocity of the fluid and decreases the pressure.

## What is a good overall heat transfer coefficient?

Convective heat transfer coefficient for some common fluids: Air – 10 to 100 W/m2K. Water – 500 to 10 000 W/m2K.

What is a good heat transfer coefficient?

As mentioned earlier in the article the convection heat transfer coefficient for each stream depends on the type of fluid, flow properties and temperature properties. Some typical heat transfer coefficients include: Air – h = 10 to 100 W/(m2K) Water – h = 500 to 10,000 W/(m2K).

### 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.

Why does heat transfer coefficient increase with flow rate?

As our common sense suggests, more the velocity, more the rate of mass transfer and hence more is the rate of convective heat transfer. Hence heat transfer coefficient increases with the increase in the velocity of the fluid.

#### What factors affect the value of the heat transfer coefficient and how do these factors affect H increase or decrease )?

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).

What does a higher heat transfer coefficient mean?

The overall heat transfer coefficient is influenced by the thickness and thermal conductivity of the mediums through which heat is transferred. The larger the coefficient, the easier heat is transferred from its source to the product being heated.