Standard Operating Procedure for the
One Dimensional Heat Conduction
Apparatus
Located in Rm. H-17 Head Hall
Prepared
10th May, 2010
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Table of Contents
1. Scope ........................................................................................................................................4
1.1 Objective ............................................................................................................................4
1.2 Regulations ........................................................................................................................4
2.Apparatus Overview and objective ...........................................................................................4
3. Hazards evaluation and controls ..............................................................................................7
3.1 Possible fire event ..............................................................................................................7
3.2 Ventilation..........................................................................................................................7
3.3 Kinetic, thermal & accoustic..............................................................................................8
3.4 Electrical ............................................................................................................................9
3.5 Water ..................................................................................................................................9
3.6 General concerns ................................................................................................................9
4. Operation..................................................................................................................................9
4.1 Qualified personnel ............................................................................................................9
4.2 Experiment preparation......................................................................................................9
4.3 Lab instructions ................................................................................................................11
4.4 Operating procedure.........................................................................................................13
5. Typical test .............................................................................................................................14
Appendix A: Experiment field notes sheet ................................................................................16
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H-17, Head Hall Floor Plan
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1.1 Objective
This standard operating procedure is intended to provide operating instructions and
safety information for the Department of Mechanical Engineering’s One
Dimensional Heat Transfer Experiment located in H-17, Head Hall. This document
is intended a guideline and a supplement to proper training that must be provided
by qualified personnel before the unit is operated.
1.2 Regulation
This document has been developed in accordance with the Environmental Health
and Safety Office of the University of New Brunswick.
2. Apparatus Overview and Objective
The experimental apparatus is designed to measure the thermal conductivity of a
test sample. The device consists of a frame that allows a solid sample of fixed
dimension to be held between a heat source or hot plate and a heat sink or cold
plate. The objective is to have the heat travel from the heat source through the test
material into the cold plate. The unit is arranged with the hot plate in the center and
the material to be tested on either side of it. The test material in turn has the cold
plate on its other side. There is an array of thermocouples to monitor the
temperatures at various points on the apparatus. This assembly is held together in
compression by a threaded rod through the frame. The hot plate is made up of two
separate Nichrome heating wires, each with their own separate power supplies. The
heater wires are wound around a sheet of electrically insulating mica then
sandwiched between two more sheets of mica. This allows the heater assembly
(hot plate) to be placed between the two brass plates without shorting out the
heating wire. Of the two separate heaters the one in the center is referred to as the
main heater and has an area of 6” x 6”. It has a DC power supply and the voltage
and current supplying it are monitored. The annular heater that surrounds the main
heater is called the guard heater and it has an AC voltage supply. There is actually
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a small soldered gap between the center and outer plate. The overall size of the
brass hotplate is 12” x12”.
The objective of the guard heater is to ensure the outer perimeter of the brass hot
plate is the same temperature as the center section of the brass plate. This uniform
temperature distribution ensures that any power input to the main heater does not
travel across into the guard and vice versa. If there is uniform temperature across
the entire brass plate we can then say that any heat transfer from the main heater is
normal to its plane, through the test sample and in the cold plate. The cold plate is
made up of a hollow bass plate that has two connections for a cold water supply.
The cold water enters through the bottom of the plate and exits through the top
connection. See Figures 1 and 2 for details.
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Figure 1: Unit Schematic
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Figure 2: One Dimensional Heat Transfer Apparatus
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3. Hazard Evaluation and Controls
3.1 Possible Fire Event
In the event of a fire evacuate the room immediately. Pull the nearest fire alarm
(located outside room). Should you return to attempt to extinguish the fire do not
do so alone and make only one attempt. Leave immediately if unsuccessful. If
successful stay at the scene and have someone alert Security (ph. # 4830) and the
Environmental Health Safety office (ph. # 5075).
3.2 Ventilation
Ventilation fans and ductwork are installed such that there shall be fresh air
introduced into the room (green duct) and ambient air exhausted from the room
(teal duct) at all times the room is occupied. These fans are controlled by wall
switches locally (see Figure 3) but are on over-ride controls controlled by Facilities
Management (FM). If at any time the fresh air supply or room exhaust fans are not
working contact FM immediately (ph # 4889). There is a household CO monitor
mounted on the north pillar. Ensure that it is operational by observing the moving
LCD display.
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Figure 3: Ventilation Controls.
3.3 Kinetic, Thermal and Acoustic
There are no moving parts involved with this experimental apparatus.
The unit itself when operated properly should not exceed 40 °C so the risk is
minimal. If at any time the unit smells hot or smoke appears switch off and unplug
both power supplies and notify the instructor.
If there is any other equipment being operated that requires hearing protection then
disposable earplugs are to be worn by students, instructors and all other room
occupants. Instructors are responsible for relaying this information onto all
involved.
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3.4 Electrical
The hot plate involved in this experiment is electrically supplied as are the
instruments monitoring it. Do not touch any electrical cable while they are
energized. Examine the unit for frayed or bare wires regularly before it is operated.
3.5 Water
Ensure there are no water leaks at any of the connections. Examine the hoses for
and sharp bends or kinks.
3.6 General Concerns
If at any time during the engines startup, operation or shut down it should behave
erratically different than normal notify the technician or faculty member. This may
include, but is not limited to, strange noises, smoke, smells, vibrations, elevated
temperatures or leaks of any kind.
4. Operation
4.1 Qualified personnel
The following text will provide a guideline for correct operation of the apparatus.
These instructions are used to augment the one on one instruction that has already
been provided by trained personnel. Only after the individual has been trained and
feels confident in with the engines startup, operation and shutdown procedures
should they attempt to operate the engine using these notes.
Do not proceed if you are not properly trained or are unsure in any manner of the
engines operation and safety concerns.
4.2 Experiment Preparation
This experiment should be set up at least 6 hours prior to the lab period and be
closely monitored to ensure the system reaches equilibrium.
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Make sure the cold water is flowing freely and equally through both cold plates.
Observe the outlet of each plate as the combine and enter the sink drain via the
transparent hoses.
Do not over-pressurize by opening the supply valve faucet too far. There only
needs to be a low constant flow through the plates, enough to ensure there are no
air locks. Air locks in the cold plates or supply and drain lines may affect adequate
and even flow.
The flow rate when checked with a measuring vessel and stopwatch should be
around 5 liters per minute.
Observe the cold point temperatures to ensure they are at or near the same value,
this will confirm that there is an even water flow through the cold plates.
To achieve a given temperature gradient across a test sample set the main heater
supply using the DC power supply with a value somewhere between 0 and 10 volts
DC.
Control the guard temperature by adjusting the guard heater power supply (Variac)
dial between 0-25 % of 120 VAC.
Keep in mind that the specimen material, specimen thickness and desired
temperature change across it all play a role in determining the power input to each
heater.
The thermocouples should be monitored regularly and the power supplies adjusted
accordingly. Make small changes in the power supplies and keep a log of the
changes made and temperatures achieved. Let the system reach steady state after
each change. Try to get the hot plate as uniform in temperature as possible.
Once the values of the main heater and guard heater power inputs are established
document them.
For example the setting for main heater supply when using a sample of 1” thick
high density polystyrene is 6.0 VDC @ 200mA. The guard heater is set at 16 % of
120 VAC. This yields ~20°C temperature difference across the specimen.
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On completion of the lab simply switch off each power supply. This will maintain
the dial settings for the next run. When the system is run again simply turn them
on.
Typically the system is started the previous day or early that morning for a mid
afternoon session.
See that there is a good supply of ear plugs. Let the technician know if the supply
is low.
4.3 Lab Instruction
4.3.1 Instructor Responsibilities
The lab script should be read and understood. The material specifics and
experimental parameters should be outlined in that document.
The lab instructor shall remain in the room while the experiment is in progress.
After the full group has assembled and before any explanation has begun the
instructor should relay all safety precautions as outlined in section 3. Inform them
that they must contact the instructor should any problems or concerns arise during
the experiment. Make the group aware of the fire extinguisher locations and exits.
4.3.3 Data/Instrument Locations and Functions
Refer to the following figures for the necessary data collection points and
instrument locations.
- DC power supply (Main Heater supply). Figure 4.
- DC ammeter (Main Heater current). Figure 4.
- DC voltmeter (Main Heater voltage). Figure 4.
- AC power supply (Guard Heater supply). Figure 4.
- Digital Thermometer to monitor the 10 type “T” thermocouples across the system
and selector switch. Figure 5.
- Thermocouple selector switch whose temperature points are as follows:
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1- Cold point 1(left side)
6- Main Heater 4 (right/rear)
2- Cold point 2 (right side)
7- Guard Heater 1(right/front)
3- Main Heater 1(right/front)
8- Guard Heater 2 (left/front)
4- Main Heater 2 (left/front)
9- Guard Heater 3(left/rear)
5- Main Heater 3 (left/rear)
10- Guard Heater 4 (right/rear)
Figure 4: Power supplies and meters.
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Figure 5: Digital thermometer and switch
4.4 Operating Procedure
4.4.1 Startup
The startup procedure should take place several hours before the lab period. The
experimental power inputs should have already been established based on the
desired temperature difference. Once these inputs are known, leave the voltage
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adjustment knobs set in position and just power off both supplies via the on/off
switch. Once again ensure even water flow to and from the cold plates.
Ensure the digital thermometer is set to “type T” thermocouples via the selection
push button and set the units to F° or C° as desired. Leave the digital thermometer
powered off when not in use to conserve battery power.
Turn on the digital voltmeter and set to read DC volts.
Turn on the ammeter and set to read DC amps.
4.4.2 Shutdown
Ensure the water is shut off at the source (sink faucet).
Turn off both power supplies.
Turn off the voltmeter, ammeter and digital thermometer.
5.0 Typical Tests
The actual test procedure will be outlined in the lab script as issued by the
professor. The material dimensions will also be given. The typical test however
usually consists of four trials five minutes apart. All 10 temperatures and the main
heater voltage and current are noted. The material type and dimensions will be
given by the instructor. A sample field notes sheet is given in appendix’A’
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Appendix ’A’
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