Quick answer. Buy rigs that let a student close the energy balance. Each of HTL-0001 to HTL-0013 is a steady-state experiment: energy in through a controlled, measured heater, energy out along the path being studied, and energy lost to the room. If any of the three cannot be measured, the result has no check on it. So ask of every rig how input power is held steady and read, whether flow is measured on both streams of an exchanger, and how lagging or a guard heater deals with losses. Then ask how long each rig takes to reach steady state, because that decides whether it fits your practical slot.
Thirteen experiments, coded HTL-0001 to HTL-0013, covering the three modes of heat transfer and the equipment that uses them. Conduction: heat transfer through a composite wall, through a lagged pipe, thermal conductivity of a metal rod and thermal conductivity of an insulating powder. Convection: natural convection and forced convection apparatus. Radiation: an emissivity measurement apparatus and a Stefan-Boltzmann apparatus. Phase change and exchangers: dropwise and filmwise condensation, a parallel and counter flow heat exchanger, a shell and tube heat exchanger, and a heat pipe demonstrator.
Two records carry spelling errors in our catalogue - the radiation law is Stefan-Boltzmann and the exchanger experiment is parallel flow - and two thermal conductivity records appear to describe the same experiment. The apparatus is the standard set; quote the code and the full product name together and ask for the experiment list of each record you are choosing between.
Every experiment in this listing is a steady-state energy balance, and that single fact should decide which rigs you buy and how you specify them. A student should be able to account for the energy put in, the energy that left by the path being studied, and the energy that leaked away somewhere else. A rig that cannot support that accounting produces a number with no way of knowing whether it is right. So ask of every rig: what is measured on each energy path, and what is done about the losses?
| Energy path | What must be measurable | What goes wrong when it is not |
|---|---|---|
| In | Electrical power to the heater, by voltmeter and ammeter or a wattmeter, with a controller that holds it steady | A heater on an uncontrolled supply drifts with mains voltage, and the input is then an assumption |
| Out, by the intended path | Temperatures at known positions, and for the exchangers, flow rate on both streams | With flow measured on only one side of a heat exchanger the energy balance cannot be closed, which is exactly the comparison the experiment exists to teach |
| Lost | Lagging, and ideally a guard heater; at minimum, enough thermocouples to show the loss | An unlagged conduction rig sends a significant fraction of its input into the room, and the calculated conductivity comes out wrong in a way that looks like a property of the material |
Surface temperature is the hardest quantity to measure in a teaching heat transfer laboratory, and most of the scatter in student results comes from it rather than from the theory. A thermocouple reads its own junction temperature, not the surface it is near; a junction standing off a hot wall in moving air reads low, and one embedded in a drilled pocket with no thermal contact reads low too.
So ask, for every rig: how many thermocouples are fitted and exactly where; how they are attached - peened into a groove, soldered, clamped or merely pushed into a hole; what type they are and what the cold junction arrangement is; and how they are read. A selector switch and a single display is the economical arrangement and makes a student take readings one at a time while the rig drifts; a multi-channel logger takes them simultaneously and is worth the difference on the exchanger and transient experiments. Ask whether a data logging option exists and what it costs, because it is hard to add to a frame later.
And ask the question that decides your timetable: how long does each rig take to reach steady state? A conduction rig that needs ninety minutes to settle cannot be used in a two-hour practical with any time left for readings, while one that settles in twenty can. This is the single most useful question to put to us about this range, and the answer is rarely on a specification sheet.
Stefan-Boltzmann. The law is a fourth-power relationship, which has a consequence students should meet explicitly: a small error in absolute temperature becomes a large error in radiated flux. A one per cent error in absolute temperature gives roughly four per cent in flux. That makes thermocouple calibration and the use of absolute temperature - not degrees Celsius - central to this experiment rather than a formality. Ask what temperature range the apparatus reaches, how the hot enclosure is heated and timed, and what shielding protects the operator.
Emissivity. The usual method compares a blackened plate and a test plate at equal electrical input and finds the temperature difference. Ask what test surfaces are supplied and whether further specimens can be fitted, because the interesting lesson is the comparison between a polished and an oxidised surface of the same metal.
Parallel and counter flow heat exchanger. This is the classic exercise: the same exchanger, the same flows, two flow arrangements and two quite different temperature profiles, from which the log mean temperature difference and the overall coefficient follow. Two requirements make or break it: the flow direction must be reversible by valves without re-plumbing, and both streams must have measured flow. Ask also for enough thermocouples to plot the profile along the exchanger rather than only at the ends - a four-point profile on each stream turns a calculation into a picture.
Shell and tube. Industrially the most important configuration, and the one where the student meets baffles and the difference between shell-side and tube-side coefficients. Ask how many tubes and passes, whether the shell can be opened for inspection, and what the maximum temperature and pressure are.
Dropwise and filmwise condensation. The most visually convincing experiment in the range - two tubes, one promoting drops and one a film, with a large difference in heat transfer coefficient. One honest limitation to know before buying: a dropwise surface depends on a promoter or a surface treatment, and that treatment degrades with use and time, after which the tube condenses as a film like its neighbour. Ask how the dropwise surface is produced, how long it lasts in service, whether it can be renewed and what a replacement tube costs. This rig usually uses steam, which brings the safety note below.
The heat pipe demonstrator is the one item here that produces an audible reaction in a class, provided it is compared directly with a solid rod of the same diameter and length. Ask whether a comparison rod is supplied, and what working fluid and temperature range the pipe uses.
Three things to settle before installation. Steam is the serious hazard in a heat transfer laboratory, not hot metal: a steam burn is worse than a touch on a hot surface, a leak from a steam fitting can be invisible for the first few centimetres, and any steam generator is a pressure vessel with statutory inspection requirements in many countries. If the condensation or exchanger rigs are steam-heated, ask what generator is supplied, what certification it carries and what your own authority requires. Hot surfaces need guards or clear marking and a cool-down rule before dismantling - and students should be told that a surface that looks cold after fifteen minutes is not. Water and electric heaters share these benches, so earth-leakage protection on every outlet is not optional, and a drip tray belongs under anything circulating water.
For each rig: the experiment list and the quantities measured; heater rating and how input power is controlled and measured; number, type, position and attachment of thermocouples, and how they are read; flow measurement on each stream; lagging and any guard heating; time to steady state; temperature and pressure limits; whether a data logging option exists and its price; services required - power, water supply and drain, steam, ventilation; bench or floor mounting, mass and footprint; consumables and spares with prices, which here means thermocouples, heaters, tubes, insulation and seals; calibration certificates for thermocouples and instruments; and the warranty, commissioning and local service position. For any certification stated here, contact us for the latest copies of the relevant certificates before you tender on it.
Related ranges: machines for thermodynamics, steam and power plant apparatus, refrigeration and air conditioning for the vapour compression cycle and heat pumps, chemical reaction engineering for fluidised bed heat transfer and process units, process control and instrumentation for temperature control, and cutaways models for the engine test rigs where a heat balance is the exercise. The full set is listed under engineering apparatus. For a quotation, tell us the destination country, your syllabus experiment list, the class size in one practical session and the length of your practical slot - that last answer changes which rigs we recommend.
An energy balance a student can close. Input power should be read by voltmeter and ammeter or a wattmeter, with a controller that holds it steady; a heater on an uncontrolled supply drifts with mains voltage and the input becomes an assumption. Output needs temperatures at known positions and, for the exchangers, measured flow on both streams. Losses need lagging, ideally a guard heater, and enough thermocouples to show the loss. An unlagged conduction rig sends a significant fraction of its input into the room, and the calculated conductivity then comes out wrong in a way that looks like a property of the material.
Surface temperature is the hardest measurement in a teaching heat transfer laboratory, and most scatter in student results comes from it. A thermocouple reads its own junction: one standing off a hot wall in moving air reads low, and so does one pushed into a drilled pocket with no thermal contact. Ask how many are fitted, exactly where, and how they are attached: peened into a groove, soldered, clamped or merely pushed into a hole. A selector switch with one display forces readings one at a time while the rig drifts; a multi-channel logger reads simultaneously and is hard to add to a frame later.
Ask this for every rig, because it decides your timetable and the answer is rarely on a specification sheet. A conduction rig that needs ninety minutes to settle cannot be used in a two-hour practical with any time left for readings, while one that settles in twenty minutes can. When you ask for a quotation, give us your syllabus experiment list, the class size in one practical session and the length of your practical slot. The slot length in particular changes which rigs we recommend, and it is the single most useful thing to tell us about this range.
The Stefan-Boltzmann law is a fourth-power relationship, so a small error in absolute temperature becomes a large error in radiated flux: one per cent in temperature gives roughly four per cent in flux. That makes thermocouple calibration, and working in absolute temperature rather than degrees Celsius, central to the experiment. Ask what temperature range the apparatus reaches, how the hot enclosure is heated and timed, and what shielding protects the operator. For emissivity, which compares a blackened plate with a test plate at equal input, ask what test surfaces are supplied and whether a polished and an oxidised surface of the same metal can be fitted.
For the parallel and counter flow exchanger, the lesson is the same exchanger and the same flows giving two different temperature profiles, from which the log mean temperature difference and the overall coefficient follow. Two requirements make or break it: flow direction must be reversible by valves without re-plumbing, and both streams must have measured flow. Ask for enough thermocouples to plot the profile along the exchanger, not just at the ends; a four-point profile on each stream turns a calculation into a picture. For the shell and tube exchanger, ask the number of tubes and passes, whether the shell opens for inspection, and its temperature and pressure limits.
Dropwise and filmwise condensation is the most visually convincing experiment here, but the dropwise surface depends on a promoter or surface treatment that degrades with use, after which the tube condenses as a film like its neighbour. Ask how the surface is produced, how long it lasts, whether it can be renewed and whether replacement tubes are available. The rig usually uses steam, the serious hazard in this laboratory: a steam burn is worse than a hot surface, and any steam generator is a pressure vessel with inspection requirements in many countries. Ask what generator is supplied, and fit earth-leakage protection on every outlet.
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.
Specifications for HTL-0001 to HTL-0013, including heater rating, thermocouple number and attachment, flow measurement, time to steady state and temperature and pressure limits, are confirmed in writing on the quotation. For steam generator, thermocouple or instrument documents, contact us for the latest copies of the relevant certificates. No price is quoted on this page. Listing note: this range is a strict subset of another category on this site, whose first 13 products are these same 13 items under identical HTL codes, so the same products appear on two pages; two records misspell Stefan-Boltzmann and parallel flow; and two thermal conductivity records appear to describe the same experiment.
To gauge the real rate of warmth exchange through the composite chambers from the deliberate interface temperature of the two protecting materials with known warm conductivities.ø To decide the successful warm conductivity of the composite cylinder.ø To look at the hypothetical temperature profile inside the composite barrels, with that of watched profile
Experimentation:Determination of the Emissivity of a test plate and to Study the variation of emissivity of test plate with absolute temperature.
The main object of the experimental setup is to study the following at various flow rates:
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