Lee's Disc Apparatus
Holmarc's Lee's Disc Apparatus (Model : HO-ED-M-03) is designed for the measurement of thermal conductivity in bad conductors. Thermal conductivity is the property of a material that indicates its ability to conduct heat. Conduction takes place if there exists a temperature gradient in a solid (or stationary fluid) medium.
Lee's Disc Apparatus comprises of a brass disc resting on another slab of the same dimension with special heating coil. Both metallic discs have radial holes for the sensitive thermistors. Material under test is placed in between two discs. The heater is turned on and the apparatus is left idle until the temperature gets stabilized. At this point the heat energy passing through the heat sample will be exactly equal to the heat flowing out of the lower block.
Maximum temperature the disc can achieve during the experiment is around 50 degree Celsius to make it safe for handling with even bare hands. Similarly, operating voltage for heating coil sandwiched between the discs is fixed as 50 V for safety. The temperature sensors used are highly sensitive and accurate with least count as low as 0.2 degree Celsius. Front panel is equipped with digital display and keyboard for user friendly operation.
This instrument provides the facility for performing experiments using different kinds of sample materials. The front panel includes LCD display and keyboard for readouts and settings.
There are three operation modes for this Equipment - Manual mode, Auto mode and PC mode. In manual mode, the user can calculate thermal conductivity using the acquired data manually. In auto mode, the user can retrieve result directly from the system once the temperature stabilized. In PC mode, one can monitor progress of the experiment through a computer and can calculate thermal conductivity with the help of Holmarc’s software. This diversity of usage makes the equipment user friendly.
Caution : Do NOT touch the discs with bare hands during the time of heating. High temperature can make severe burns in the body. Try to use gloves for handling the discs.
Experiment:
To determine thermal conductivity of bad conductors (Glass, Nylon, Plywood, etc.) in the form of a disc using Lee's method.
Thermal conductivity,
k = (Mc dT / dt ) / (πr2 (T2 - T3) ) × (r + 2h) d / 2( r + h) W / mK-1
Where,
M = Mass of the metallic disc
c = Specific heat capacity of the metallic disc
h = Height of the metallic disc
r = Radius of the metallic disc
dT / dt = Rate of cooling of the metallic disc at T2
d = Thickness of the sample
T2 - T3 = Steady temperatures recorded at T2 and T3 respectively
Features:
| New integrated cost effective design |
| Measure thermal conductivity of different materials |
| The optics used in this device are of research quality |
| Manual mode, Auto mode and PC mode are possible |
| LCD display is provided for accurate measurement |
| D7340 ASTM Standard |
| Easy to use equipment |
| Useful for any poorly conductive material such as leather, rubber, textile, cork etc. |
Schematic:
Graph:
Learn Out:
| Thermal conductivity |
| Heat transfer |
| Specific heat capacity |
Scope of Delivery:
RS 232 PC cable and connector
Heat Sink Compound
software CD
Instruction Manual