What is LMTD for parallel flow heat exchanger?

The LMTD is a logarithmic average of the temperature difference between the hot and cold feeds at each end of the double pipe exchanger. For a given heat exchanger with constant area and heat transfer coefficient, the larger the LMTD, the more heat is transferred.

What is parallel flow heat exchanger?

In heat exchanger. This flow arrangement is called parallel flow. Heat is transferred from the warm fluid through the wall of the inner tube (the so-called heating surface) to the cold fluid. A heat exchanger can also be operated in counterflow, in which the two fluids flow in parallel but opposite directions.

What is difference between LMTD and 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).

What is LMTD equation?

LMTD = ((100 – 30)-(90-50)) / ln (100-30/90-50) = 53.6 degree Celsius . 2. For a Counter Flow Heat Exchanger for same data calculate the LMTD .

How do you calculate lmtd?

Formula for LMTD calculation – For a Parallel Flow Heat Exchanger, Hot fluid entering at temperature 100 degree Celsius and exiting at 90 degree Celsius . Cold fluid Entering at 30 degree Celsius and exiting at 50 degree Celsius. Find the LMTD . LMTD = ((100 – 30)-(90-50)) / ln (100-30/90-50) = 53.6 degree Celsius .

How do you calculate LMTD?

What is the unit of LMTD?

The LMTD is a logarithmic average of the temperature difference between the hot and cold streams at each end of the exchanger. The larger the LMTD, the more heat is transferred. The use of the LMTD arises, straightforwardly, from the analysis of a heat exchanger with constant flow rate and fluid thermal properties.

Why is NTU more accurate than LMTD?

The NTU method does not rely on using an numerical iterative solution to find the outlet temperatures of the heat exchanger, which would be the case if the LMTD method were used to find two outlet temperatures. Thus, the NTU would save much calculation time in this case.

What is significance of LMTD in heat exchanger design?

What is LMTD in a heat exchanger?

Logarithmic Mean Temperature Difference (LMTD) is an indicator of the average temperature difference between the hot and cold fluids in a heat exchanger. As can be seen from the equation, LMTD uses the logarithmic mean of the temperature differences instead of an arithmetic mean.

What is the MTD formula for heat exchanger design?

Mean Temperature Difference, F Factors We will use the Mean Temperature Difference (MTD) formulation for design of heat exchangers in this Manual. The MTD is related to the Logarithmic Mean Temperature Difference (LMTD) by the equation MTD=F(LMTD) (2.10)

What is the use of parallel flow heat exchanger?

The parallel flow heat exchanger is mainly used where limited transfer of heat is recommended.The limit of the exit temperature of cold fluid is exit temperature of hot fluid in case of parallel flow heat exchanger.

Which LMTD is strictly applicable to a parallel flow exchanger?

LMTD given by Eq (10.6) is strictly applicable to either parallel flow or counter flow exchangers.

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