The plate heat exchanger experiment determines the heat duty, log mean temperature difference (LMTD), overall heat-transfer coefficient, and effectiveness of a plate-type exchanger in both parallel- and counter-flow. Plate heat exchangers deliver very high heat transfer in a compact size, which is why they dominate dairy, HVAC, and process cooling.
Aim of the experiment
To determine the LMTD, overall heat-transfer coefficient (U), and effectiveness of a plate heat exchanger in parallel and counter flow.
Theory and formulas
The heat lost by the hot fluid equals the heat gained by the cold fluid:
- Q = mh ch (Th,in − Th,out) = mc cc (Tc,out − Tc,in)
- LMTD: ΔTlm = (ΔT₁ − ΔT₂) / ln(ΔT₁/ΔT₂)
- Overall coefficient: U = Q / (A · ΔTlm)
- Effectiveness: ε = Qactual / Qmax, where Qmax = Cmin(Th,in − Tc,in)
For the same terminal temperatures, counter-flow gives a larger LMTD than parallel-flow, so it transfers more heat, the key practical takeaway.
Apparatus required
- Plate heat exchanger test rig with a corrugated plate pack
- Hot-water tank with heater and a cold-water supply
- Flow-control valves to switch between parallel and counter flow
- Flow meters and inlet/outlet thermometers on both streams
Procedure
- Set the hot and cold flow rates and switch the valves to parallel flow.
- Allow temperatures to stabilise; record all four inlet/outlet temperatures and both flow rates.
- Switch to counter flow and repeat the readings.
- Compute Q, LMTD, U, and effectiveness for each arrangement and compare.
Result
Counter-flow shows a higher LMTD, overall coefficient, and effectiveness than parallel-flow, demonstrating why industrial exchangers are run counter-flow.
Applications
Plate heat exchangers are used in dairy pasteurisation, HVAC, and chemical process heating and cooling. Compare them with the double-pipe heat exchanger and shell-and-tube heat exchanger experiments; LMTD and effectiveness are defined in the engineering lab glossary.
Frequently asked questions
Why is a plate heat exchanger more efficient than a shell-and-tube?
The corrugated plates create turbulence and provide a very large surface area per unit volume, giving a higher heat-transfer coefficient in a compact unit.
Why does counter-flow transfer more heat than parallel-flow?
Counter-flow maintains a larger and more uniform temperature difference along the exchanger, which gives a higher LMTD and more heat transfer.
What is the overall heat-transfer coefficient U?
U combines the convective and conductive resistances of the exchanger and is found from U = Q / (A · LMTD).
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Specify the heat-exchanger experiment around the energy balance
The useful result comes from stable hot- and cold-side inlet and outlet measurements, known flow rates and a declared flow arrangement. The RFQ should say whether students must compare co-current and counter-current operation, calculate LMTD, estimate an overall coefficient or study effectiveness. Sensor placement and the way flow is measured affect every calculation.
What to confirm before requesting a quotation
- Identify the required flow arrangements and plate configuration.
- Confirm temperature and flow measuring points, ranges and indication.
- State heating, cooling-water, pump and electrical requirements.
- Ask for the experiment method, calculation sheet and included hoses or valves.
For an international order, also state the quantity, destination, electrical supply, documentation, installation or training needs and requested delivery basis. Treat catalogue information as a starting point; the current model page, datasheet and written quotation must confirm the exact configuration.
Plate heat exchanger trainer: measurements and operating scope
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