Quick Answer: Critical Radius Of Insulating Material uses 4 G.I. pipes with heaters inside and plaster of Paris insulation of different thicknesses to show the radius at which heat loss from an insulated cylinder is maximum. Each heater has its own dimmerstat, with a common voltmeter and ammeter.
Last updated: October 2026
Key Features
4 G.I. pipes with electrical heater inside
Plaster of Paris insulation of different thickness over the pipes
Dimmerstat for each heater input (4 Nos.)
Common voltmeter and ammeter for heater input
Digital temperature indicator for temperatures across the insulation
Technical manual supplied
Technical Specifications
Specification
Value
Pipes
G.I., with electrical heater inside, 4 Nos.
Insulation
Plaster of Paris, different thickness
Dimmerstats
4 Nos.
Measurements
Voltmeter, ammeter, digital temperature indicator
Supply
230 V, 5 Amp, A.C., with earthing connection
Floor area
1 m x 1 m x 1.5 m height
About This Product
By controlling the input to each heater and measuring temperatures across the insulation, students show that the critical radius of insulation is the ratio of thermal conductivity to the outside heat transfer coefficient. The underlying idea, demonstrated here for the HEAT TRANSFER LAB, is that at a particular radius of insulation over a cylinder the loss of heat is maximum.
Frequently Asked Questions
Q1. What does the critical radius apparatus demonstrate? That at a particular radius of insulation over a cylinder the heat loss is maximum, and that this critical radius is the ratio of thermal conductivity to the outside heat transfer coefficient.
Q2. What insulation is used on the pipes? Plaster of Paris insulation of different thicknesses on the outside surface of the G.I. pipes.
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