Heat Transfer Lab Equipment Lab Equipment Manufacturer, Supplier and Exporter in India

Heat Transfer Lab Equipment and Test Rigs

The framework: account for every watt that leaves

A heat transfer experiment is an energy balance. The student measures the electrical power into a heater and some temperatures, and calculates a conductivity, a coefficient or an emissivity on the assumption that the measured power went where the theory says it went. It never all does. Some leaves through the mountings, some down the thermocouple wires, some off the back of the specimen, some by radiation when the calculation assumed only convection.

There are only three honest ways to deal with a loss, and one dishonest one.

• Guard it. Arrange the apparatus so the loss path carries no heat, because there is no temperature difference across it. This is what the word guarded means on a guarded hot plate: a surrounding guard heater is held at the same temperature as the main heater, so no heat flows sideways and all the measured power goes through the specimen. It is the most expensive solution and the only one that removes the error rather than correcting for it.
• Measure it. Instrument the loss path and subtract. A thermocouple at the far end of a conductivity rod tells you what is leaving the end; a thermocouple on the outside of the lagging tells you what is leaving radially.
• Bound it. Show by calculation that the loss is small compared with the flow being measured, and quote the bound. This is legitimate and it is what good lab manuals do, but it only works if the bound is actually computed rather than asserted.
• Ignore it. The default. It is the reason a student measuring the thermal conductivity of brass reports a value well below the book figure, concludes the apparatus is broken, and learns nothing - when in fact the apparatus behaved exactly as physics requires and the equation was the thing that was wrong.

The teaching value of this equipment is in making students confront that fourth option. A rig that hides its losses produces tidy numbers and no understanding. A rig that exposes them - by giving the student the extra thermocouples and asking for a loss estimate - produces a worse-looking result and an engineer. Specify for the second.

What each experiment actually measures, and what it loses

Read this column by column rather than row by row. The third column is the one a quotation never mentions and the one that decides your data.

Steady state is a decision, not an event

Almost every experiment in this listing is a steady-state measurement, and the single most common procedural failure is that readings are taken when the timetable runs out rather than when the apparatus has settled. A heavily lagged pipe or a thick insulating slab has a long time constant by design - the better the lagging, the longer the wait - so the apparatus that gives the cleanest result is the one students are most likely to read too early.

The fix is to make steady state a stated criterion rather than a judgement. A department should write a tolerance into the lab sheet: for example, no measured temperature changing by more than 0.2 °C over five minutes, on at least three consecutive readings. The particular numbers belong to your apparatus and your tolerance for lab time, and should be established once by running one experiment to true equilibrium and watching the approach; the point is that a criterion exists and is written down, so that a student who is running late has to record that the criterion was not met rather than quietly taking the reading anyway.

Two practical consequences for specification:

• Ask for a data logger, or at least a timer and a tabulated reading sheet, on the slow experiments. A rig with a multi-channel logger lets a class start an experiment, do something else, and come back - which is the only way a two-hour time constant fits in a one-hour slot.
• Prefer a heater with a stable, measurable input over a powerful one. Steady state is reached sooner at low power, the losses are smaller in absolute terms, and a dimmerstat plus a true-RMS wattmeter reading is worth more than a bigger element. Ask what the power measurement is: a voltmeter and ammeter on a phase-angle-controlled supply do not multiply to give the real power.

The thermocouple arrangement is the measurement

On this equipment the sensors are not an accessory. Every number the student calculates is a difference between two temperatures, so an error in one reading propagates straight into the result, and the usual errors are mechanical rather than electrical.

• Embedded, not resting. A junction in a drilled hole with thermal paste or a press fit reads the metal. A bead taped to a surface reads something between the surface and the air, and on a hot surface in still air that can be far from the surface temperature. Ask how each junction is mounted, specimen by specimen.
• Type, and why. Type K (nickel-chromium against nickel-aluminium) covers the whole range of this equipment comfortably and is the sensible default. Type J (iron against constantan) is cheaper and adequate at lower temperatures but the iron leg corrodes. Mixing types on one selector switch without matching the compensation is a classic source of a constant offset on some channels and not others.
• Count the channels you actually need, including the ones for the losses: surroundings temperature for anything radiating, lagging-surface temperature for anything lagged, inlet and outlet on both sides of any exchanger, and the far end of any conductivity rod. A rig sold with six channels for an experiment that needs eight will be used with six.
• Calibration is a purchasable experiment. A thermocouple calibration rig turns a maintenance task into a lab exercise, and it is the honest answer to a student who asks how we know the thermocouple is right. If your department is buying a set, one calibration rig serves the whole set.

Two experiments that are nearly always sited wrongly

Natural convection

A natural convection apparatus beside a door, under a ceiling fan, or in front of an air conditioner is a forced convection apparatus. The whole experiment rests on the air moving only because the surface heated it, and a draught of a fraction of a metre per second is enough to change the coefficient materially. This is worth deciding before the bench layout is fixed: the natural convection rig wants a corner away from doors and vents, and ideally a shield or enclosure. It is also the experiment where the radiation term is largest relative to the convection being measured, so the surroundings thermocouple is not optional - without it the student is attributing radiation to convection and getting a coefficient that is too high.

Dropwise and filmwise condensation

The teaching point is spectacular - the coefficient changes by an order of magnitude between the two modes on the same surface - and it is destroyed by air in the shell. Non-condensable gas blankets the condensing surface and collapses the coefficient, so a rig without a proper vent and a written purge procedure will show a difference far smaller than the real one, or none. Ask specifically how the shell is vented and what the start-up procedure is.

Heat exchangers: the energy balance is the built-in self-check

Every exchanger rig in this listing gives the student a free check on their own data, and most lab sheets do not use it. The duty calculated on the hot side and the duty calculated on the cold side are measurements of the same quantity, so they should agree within a stated tolerance.

• If they do not agree, suspect the flow measurement first. Temperatures are easy and flows are hard. A rotameter is calibrated for a stated fluid at a stated temperature and density; running hot water through a float calibrated for cold water gives a reading that is wrong in a direction most students will not question. Ask what the calibration conditions are, and prefer a measuring tank and stopwatch as the reference method for at least one point.
• Lag the pipework, not just the exchanger. On a small rig the pipe runs can have comparable surface area to the exchanger, and the loss from them appears as a failure of the energy balance that students will blame on the exchanger.
• Parallel against counter flow is the experiment, not the exchanger type. A rig with valved reversal lets one unit teach both and makes the LMTD comparison immediate; two separate units teach the same thing at twice the cost and with the configurations never compared on the same day under the same conditions. If you buy one exchanger for a teaching lab, buy the one that reverses.
• Effectiveness-NTU is the better framing for a design course, and it needs the same measurements, so a rig adequate for LMTD is adequate for both - but check that the manual actually covers it, because many do not.

Specifying a set for a class

As with any teaching laboratory, specify by ratio rather than by item. Decide the class size, the batch size at one rig, and the number of weeks in the rotation; those three numbers determine how many of each experiment you need, and the answer is almost never one of everything.

A defensible core for an undergraduate heat transfer course, in buying order:

1. Conduction: composite wall or insulating slab, and a metal rod. These establish the series-resistance idea and the loss problem.
2. Convection: natural and forced, and the pin fin which bridges the two. Duplicate these first when the class grows, because they are the most used.
3. Radiation: emissivity comparison and Stefan-Boltzmann. One of each is usually enough.
4. Application: one reversible exchanger, plus a shell-and-tube or plate unit if the course covers industrial equipment.
5. Everything else - evaporators, heat pipe, unsteady state, critical radius, agitated vessel - is a second phase, bought against specific syllabus requirements rather than to fill a lab.

Shared services matter more than any single rig: a stable supply, a reliable cooling-water supply at a known temperature, and a data logger used across rigs. See shared engineering lab instruments for the pumps, gauges and general instruments these rigs assume you already have.

What a quotation must state

• Heater rating and how power is measured - element wattage, the controller type, and whether the instrument reads true power.
• Thermocouple type, count, and mounting method for each junction, including any channel provided for losses or surroundings.
• The guard arrangement, where the method depends on one, and whether the guard has independent control.
• Insulation material and thickness, and whether the apparatus provides a means to measure the loss through it.
• Flow measurement device, its range, and its calibration fluid and temperature.
• Services required - supply voltage and phase, cooling water flow and pressure, compressed air, drainage.
• Bench footprint and working height, and whether the unit is free-standing or needs a bench.
• What is included - specimens, spare elements, the manual, and whether sample calculations with real data are provided.

About this listing - read before you order by code

We would rather say this than let you discover it halfway down page four. This listing holds 57 records, HTL-0001 to HTL-0057, which resolve to roughly 22 distinct experiments. Several experiments appear three times under different codes - the emissivity apparatus, the Stefan-Boltzmann apparatus, the pin fin, the forced convection unit and the dropwise/filmwise condensation unit each have three records. Two codes are used twice over (HTL-0039 and HTL-0045), HTL-0034 is missing, and a few names carry typing errors that have travelled with the data: Insulting Powder for insulating, Citical Radius for critical, Parrallel, and Stefan Boltzman. One record, HTL-0049 Heat Transfer Sheet, is not a product.

So do not order by code from this page. Tell us the experiment and the class size and we will quote the current model, confirm the specification in writing, and tell you which code it ships against. We have recommended internally that this listing be consolidated, and the duplicate records removed rather than renamed.

Related ranges

Within physics lab for engineering students: thermodynamics for compressors, calorimeters, steam and refrigeration-cycle rigs, hydraulics for the bench, Bernoulli and notch experiments, and analytical instruments for pH, conductivity and photometry. Momentum transfer lab equipment covers the fluid-flow side of the same transport-phenomena syllabus. The full engineering lab equipment category lists the rest.

Frequently asked questions

Why does a student measuring thermal conductivity get a value below the book figure?

Because heat left by a path the equation ignored, and almost always radially through the lagging rather than axially along the rod. The measured power is divided by a gradient that is steeper than the axial flow alone would produce, so the conductivity comes out low. The apparatus is usually working correctly. The fix is not a better rig but a better calculation: measure the lagging surface temperature and the far-end cooling duty, estimate the loss, and subtract it. That estimate is the most valuable thing in the experiment.

What does "guarded" mean on a hot plate apparatus, and is it worth paying for?

A guard heater surrounds the main heater and is held at the same temperature, so there is no sideways temperature difference and no sideways heat flow - which means all the measured power goes through the specimen. It removes the error instead of correcting for it, and it is the recognised method for insulating slabs. It is worth paying for if you need defensible conductivity values or you teach the standard method. If the aim is to show that insulation resists heat flow, an unguarded apparatus with honest loss accounting teaches that at lower cost.

How long should an experiment take to reach steady state?

Longer than the timetable allows, which is why it needs a written criterion rather than a judgement. Establish it once by running an experiment to true equilibrium and watching the approach, then write a tolerance into the lab sheet - no temperature changing by more than a stated amount over a stated interval, on several consecutive readings. Well-lagged apparatus takes longest, so your cleanest experiment is the one most likely to be read too early. Running at lower heater power shortens the wait and shrinks the losses at the same time.

Where should the natural convection apparatus be installed?

In a corner away from doors, windows, ceiling fans and air-conditioner outlets, ideally with a shield or enclosure. The experiment assumes the air moves only because the surface heated it, and a slight draught turns it into a forced convection experiment with an unknown velocity. Decide this before the bench layout is fixed, and specify the surroundings thermocouple, because radiation is a large fraction of the total here and without that channel the student attributes it to convection.

How do we know a heat exchanger rig is giving good data?

Close the energy balance. The duty on the hot side and the duty on the cold side measure the same quantity, so compute both every run; a gap beyond your stated tolerance means something is wrong before any coefficient is believable. When they disagree, suspect the flow measurement rather than the exchanger - a rotameter calibrated for cold water reads wrong on hot - and check the pipework lagging. Verify one flow point against a measuring tank and a stopwatch.

Why does this category list several records that look like the same experiment?

Because it does. The listing has grown to 57 records covering about 22 experiments, with duplicate entries for the emissivity, Stefan-Boltzmann, pin fin, forced convection and condensation units, two codes used twice, and one missing code. We have said so on the page rather than leaving you to find it, and we have recommended consolidation. In the meantime, enquire by experiment and class size rather than by code, and we will confirm the model and specification in writing.

Key takeaways

• Account for every watt that leaves. Each loss must be guarded, measured, or bounded by calculation - and the fourth option, ignoring it, is what produces wrong student results on working apparatus.
• The thermocouple arrangement is the measurement. Embedded junctions, one consistent type, and enough channels to instrument the losses as well as the specimen.
• Make steady state a written criterion, not a judgement, and prefer a stable low heater power with true power measurement over a bigger element.
• Site the natural convection rig away from every draught, and buy the surroundings thermocouple with it - radiation is a large share of the total.
• Close the energy balance on every exchanger run. When the two sides disagree, the flow measurement is the usual culprit; buy the exchanger that reverses between parallel and counter flow.
• Specify by ratio - class size, batch size, weeks in the rotation - and buy conduction, convection and radiation cores before the specialist units.

About this page

Ray Export is a manufacturer and exporter of laboratory, scientific and educational equipment based at Plot No. 449, HSIIDC Industrial Area, Saha, Ambala, Haryana 133104, India. Enquiries: [email protected], +91-9817319615.

Written by Palak Mall, Senior Content Writer. Technically reviewed by Arvind Kumar, Lab Equipment Specialist, 12+ years in laboratory and testing instrumentation. Last updated: 17 October 2026.

The steady-state tolerance given in this page is an illustrative criterion for a department to set and verify against its own apparatus, not a measured property of any product. Thermocouple type characteristics are given at the level of standard reference practice; the applicable temperature range, tolerance class and compensation arrangement for a specific unit will be confirmed in writing on the quotation, as will heater ratings, insulation, flow-measurement calibration conditions, services and footprint. Record counts and product-name defects described above were read from this listing on 15 October 2026 and will change as the listing is corrected. No price is quoted on this page; prices for this equipment depend on specification, instrumentation and destination and are issued as dated written quotations.