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lmtd calculator
lmtd calculator is available here.
Use following calculator for co current flow lmtd correction.
lmtd calculator
LMTD Calculator
LMTD:
LMTD calculator for counter current flow heat exchanger is as below.
lmtd calculation for counter flow.
you can use following formula for calculating lmtd for counter current heat exchanger.
LMTD = (ΔT1 – ΔT2) / ln(ΔT1 / ΔT2)
where ΔT1 and ΔT2 are the temperature differences between the hot and cold fluids at the inlet and outlet of the heat exchanger, respectively.
Counter current flow heat exchangers are a type of heat exchanger that are commonly used in many industrial processes to transfer heat from one fluid to another. In this type of heat exchanger, the hot and cold fluids flow in opposite directions, which allows for a greater temperature difference between the fluids and thus more efficient heat transfer. One important parameter for the design and analysis of counter current flow heat exchangers is the log mean temperature difference (LMTD).
The LMTD is a measure of the temperature difference between the hot and cold fluids as they flow through the heat exchanger. It takes into account the fact that the temperature difference between the two fluids is not constant throughout the length of the heat exchanger, but varies as the fluids flow and exchange heat. The LMTD is defined as the logarithmic average of the temperature difference between the hot and cold fluids at the inlet and outlet of the heat exchanger:
LMTD = (ΔT1 – ΔT2) / ln(ΔT1 / ΔT2)
where ΔT1 and ΔT2 are the temperature differences between the hot and cold fluids at the inlet and outlet of the heat exchanger, respectively.
LMTD Calculator
LMTD:
LMTD correction factor
culation.
LMTD stands for Logarithmic Mean Temperature Difference, which is used in heat transfer calculations. It is used to calculate the heat transfer rate in heat exchangers.
The formula for LMTD correction factor is given by:
F = (LMTD actual / LMTD corrected)
Where LMTD actual is the actual logarithmic mean temperature difference and LMTD corrected is the corrected logarithmic mean temperature difference.
To calculate LMTD, the formula is:
LMTD = ((T1 – T2) – (t1 – t2)) / ln((T1 – T2) / (t1 – t2))
Where T1 and T2 are the temperatures of the hot fluid at inlet and outlet respectively, and t1 and t2 are the temperatures of the cold fluid at inlet and outlet respectively.
To apply LMTD correction factor to a heat exchanger, the formula is:
Qc = F * Qh
Where Qc is the corrected heat transfer rate and Qh is the actual heat transfer rate.
example
example of how to calculate LMTD and LMTD correction:
Suppose you have a heat exchanger with two fluids flowing in counter-current direction. The inlet and outlet temperatures of the hot fluid are 120°C and 80°C respectively, while the inlet and outlet temperatures of the cold fluid are 20°C and 70°C respectively.
Step 1: Calculate the LMTD.
LMTD = ((ΔT1 – ΔT2) / ln(ΔT1 / ΔT2)) where ΔT1 = Th1 – Tc2 and ΔT2 = Th2 – Tc1
ΔT1 = 120°C – 70°C = 50°C ΔT2 = 80°C – 20°C = 60°C
LMTD = ((50 – 60) / ln(50 / 60)) ≈ 53.7°C
Step 2: Calculate the LMTD correction factor.
LMTD correction factor = (LMTD actual / LMTD uniform)
where LMTD uniform = (ΔT1 – ΔT2) / ln(ΔT1 / ΔT2) when the heat exchanger has a uniform temperature distribution.
LMTD uniform = ((ΔT1 – ΔT2) / ln(ΔT1 / ΔT2)) ≈ 55.7°C
LMTD correction factor = 53.7 / 55.7 ≈ 0.964
Therefore, the LMTD correction factor is 0.964. This value is used to adjust the heat transfer coefficient in the heat exchanger to account for non-uniform temperature distribution.
Read Also,
difference between co current and counter current flow heat exchanger
Distillation types and design process
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