By attaching a baffle to the tube sheet you can create two shell-side passes. This flow arrangement produces a 2-4 floating head heat exchanger (2 shell-side passes and 4 tube-side passes).

A shell and tube heat exchanger is a class of heat exchanger designs. One fluid runs through the tubes, and another fluid flows over the tubes (through the shell) to transfer heat between the two fluids.

How to calculate the heat duty for heat exchangers?

1. Heat Duty (Sensible heat – No phase change) Q = M * Cp * ∆T. Where;
2. Heat Duty (Latent heat – Phase change) Q = M * λ Where;
3. Heat Duty for Multiphase streams. If you have a stream where more than one phase exists then you can calculate the heat duty using the equation below: Q = Qg + Qo + Qw.

8. When a fluid is used in a Shell and Tube heat exchanger, which one of the following is not true? Explanation: Fins are generally used to increase the Heat transfer Area when the heat transfer coefficient on that fluid side is comparatively low.

Which one is having highest value of overall heat transfer coefficient? Explanation: Overall heat transfer coefficient for air condensers is 780 W/m2 K while that of steam, alcohol condensers and air to various gases are 340 W/m2 K, 700 W/m2 K and 550 W/m2 K. 7.

The overall heat transfer coefficient (U) depends on individual heat transfer coefficients and the heat resistance offered by the tube-wall. We assume the coolant heat transfer coefficient (hcool) and the tube wall resistance remains constant.

Composition

1. = the overall heat transfer coefficient (W/(m2•K))
2. = the contact area for each fluid side (m2) (with and expressing either surface)
3. = the thermal conductivity of the material (W/(m·K))
4. = the individual convection heat transfer coefficient for each fluid (W/(m2•K))
5. = the wall thickness (m).

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.

Q = m × c × Δ T Q=m /times c /times /Delta T Q=m×c×ΔT

Calculation method

1. Heat load, Theta and LMTD calculation. Where: P = heat load (btu/h) m = mass flow rate (lb/h)
2. Heat transfer coefficient and design margin. The total overall heat transfer coefficient k is defined as: α1 = The heat transfer coefficient between the warm medium and the heat transfer surface (btu/ft2 h °F)

We can use the following equation to get the overall heat transfer coefficient for a shell & tube exchanger. Note, this overall heat transfer coefficient is calculated based on the outer tube surface area (Ao). So it must be multiplied by the Ao value for using in the overall heat transfer equation.

Thermal conductivity (often denoted by k, λ, or κ) refers to the intrinsic ability of a material to transfer or conduct heat. The rate equation in this heat transfer mode is based on Fourier’s law of heat conduction.

A k-value (sometimes referred to as a k-factor or lambda value λ) is a measure of the thermal conductivity of a material, that is, how easily heat passes across it. Typically this is important in assessing the potential for heat transfer between the inside and outside of a building.

To indicate to what extent a material is thermally insulating, the term thermal transmittance or U-value (formerly known as K-value) is used in the construction industry. The lower the U-value, the higher the heat resistance of a material, meaning the better the insulation.

Thickness or Distance The rate of heat transfer is inversely proportional to the thickness of the cup.

The rate (in W) at which heat transfers from the hotter object to the colder object increases with the temperature difference between the objects. Short Answer: The greater the temperature difference, the greater the rate at which heat transfers. Heat is transferred by one or more of three processes.

The density difference between two objects causes heat transfer. The temperature difference between two systems causes heat transfer. The pressure difference between two objects causes heat transfer.

Radiation is a method of heat transfer that does not rely upon any contact between the heat source and the heated object as is the case with conduction and convection. Heat can be transmitted through empty space by thermal radiation often called infrared radiation. This is a type electromagnetic radiation .

Convection is heat transfer due to a density differential within a fluid. As water’s temperature increases in the presence of a heat source, it will become less dense and rise. As it moves up and away from the heat source, it cools and becomes more dense and sinks.

The results show that higher temperatures lead to higher thermal conductivities and the lower is the material density, the higher is the thermal conductivity.

The thermal conductivity of a material depends on its temperature, density and moisture content.

Polyurethane foam is effective as an insulator because it has a high proportion (90 percent minimum) of non-connected closed microcells, filled with inert gas.

The thermal conductivity is not always constant. The main factors affected the thermal conductivity are the density of material, moisture of material and ambient temperature. With increasing density, moisture and temperature the thermal conductivity increases too.

K = (QL)/(AΔT)

1. K is the thermal conductivity in W/m.K.
2. Q is the amount of heat transferred through the material in Joules/second or Watts.
3. L is the distance between the two isothermal planes.
4. A is the area of the surface in square meters.
5. ΔT is the difference in temperature in Kelvin.

For measuring thermal conductivity, there are four main types of measurement setups: the guarded hot plate (GHP), the heat‐flow meter (HFM), the hot wire, and laser flash diffusivity.

The ability of a thermal insulation material to transmit heat in the presence of a temperature gradient is determined by its thermal conductivity. The results show that higher temperatures lead to higher thermal conductivities and the lower is the material density, the higher is the thermal conductivity.