How is the LMTD calculated for heat exchanger?

For co-current heat exchanger, ΔT1 = TH1 – TC1 = 100 – 30 = 700C (At first end hot and cold fluids enter the heat exchanger.) (At the other end hot and cold fluids exit the heat exchanger.) by definition given above, LMTD for counter current flow = (70-40) / ln(70/40) = 30 / 0.5596 = 53.610C.

How do you calculate LMTD correction factor?

Hence a correction factor ‘F’ must be introduced in the general heat equation and the equation is modified as Q = UA (F) LMTD. This correction factor ‘F’ depends on the number of shells of the heat exchanger and on the terminal temperatures of the heat exchanger.

How does the lmtd for a heat exchanger differ from the arithmetic mean temperature difference?

In arithmetic mean temperature difference you have to find temperature difference on whole lengh of heat exchanger. Then, find add them and divide by total number of readings and you will get your answer. In Logarithmic mean temperature difference you have to find temperature on inlet and outlet point.

What is lmtd in heat exchanger?

The logarithmic mean temperature difference (also known as log mean temperature difference, LMTD) is used to determine the temperature driving force for heat transfer in flow systems, most notably in heat exchangers.

Why we use lmtd correction factor?

Why do we use LMTD Correction factor? Explanation: In a shell and tube heat exchanger we observe both counter current and concurrent flow at different regions of the shell. This phenomenon makes the use of complete countercurrent LMTD unsuitable for calculations.

What do you mean by lmtd & NTU method?

The Number of Transfer Units (NTU) Method is used to calculate the rate of heat transfer in heat exchangers (especially counter current exchangers) when there is insufficient information to calculate the Log-Mean Temperature Difference (LMTD).

Why we use lmtd instead of arithmetic mean?

We use LMTD instead of average temperature in heat exchanger because we concern about both inlet and outlet temperature of both hot and cold fluids . Because of which, LMTD came into use. In LMTD, we include all the inlet and outlet temperature of both hot and cold fluids.