Under what conditions NTU method is used for the design of heat exchangers?

Under what conditions NTU method is used for the design of heat exchangers?

The LMTD method can be used if inlet temperatures, one of the fluid outlet temperatures, and mass flow rates are known. The ε – NTU method can be used when the outlet temperatures of the fluids are not known.

When or why NTU E method is used rather than LMTD?

In heat exchanger analysis, if the fluid inlet and outlet temperatures are specified or can be determined by simple energy balance, the LMTD method can be used; but when these temperatures are not available The NTU or The Effectiveness method is used.

What is NTU method of a heat exchanger?

Effectiveness-NTU (number of transfer units) methods are popular in heat exchanger design [1,2]. The number of transfer units (NTU = UA/(mcp)) itself is a combination of overall heat transfer coefficients, transfer area, fluid flow rate and heat capacity.

What is CMIN in NTU method?

The terms UA/Cmin is called the number of transfer units (NTU) since it is indicative of the. size of the heat exchanger, i.e. min. C. UA.

How do you calculate the number of heat exchangers on a tube?

4.0 – HEAT EXCHANGERS CALCULATIONS:

1. The main basic Heat Exchanger equation is: Q = U x A x ΔTm =
2. The log mean temperature difference ΔTm is: ΔTm =
3. (T1 – t2) – (T2 – t1) = °F.
4. T1 = Inlet tube side fluid temperature; t2 = Outlet shell side fluid temperature;
5. ln (T1 – t2) (T2 – t1)

Why LMTD is used in heat exchanger?

The log mean temperature difference (LMTD) is used to determine the temperature driving force for heat transfer in flow systems, most notably in heat exchangers. The LMTD is a logarithmic average of the temperature difference between the hot and cold streams at each end of the exchanger.

What are the limitations of lmtd method?

Assumptions and limitations However, if the specific heat changes, the LMTD approach will no longer be accurate. A particular case for the LMTD are condensers and reboilers, where the latent heat associated to phase change is a special case of the hypothesis.

What is full form of NTU?

NTU Full Form

Full Form	Category	Term
NIGATPUR	Indian Railway Station	NTU
Nephelometric Turbidity Unit	Electronics	NTU
Not Too Ugly	Messaging	NTU
Oceana (va)	Airport Code	NTU

What is meant by NTU?

NTU stands for Nephelometric Turbidity unit, i.e. the unit used to measure the turbidity of a fluid or the presence of suspended particles in water. The higher the concentration of suspended solids in the water is, the dirtier it looks and the higher the turbidity is. For example, 300 mg/l (ppm) of SS are 900 NTU.

What is difference between NTU and LMTD method?

The LMTD method is convenient for determining the overall heat transfer coefficient based on the measured inlet and outlet fluid temperatures. The ε-NTU method is more convenient for prediction of the outlet fluid temperatures if the heat transfer coefficient and the inlet temperatures are known.

What is the purpose of baffles in heat exchanger?

Baffles serve two functions: Most importantly, they support the tubes in the proper position during assembly and operation and prevent vibration of the tubes caused by flow-induced eddies, and secondly, they guide the shell-side flow back and forth across the tube field, increasing the velocity and the heat transfer …