Datasheet
9
Introduction
Design
Guide
Polyimide
Heaters
Silicone
Rubber
Heaters (foil)
Standard
Polyimide
& Rubber
Rubber
Heaters
(wire-wound)
Mica Heaters
Thermal-Clear
Heaters
All-Polyimide
Heaters
Sensors,
Controllers &
Accessories
Reference
Sal es and Support
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Designing with Thermofoil Heaters
Estimating power requirements
The total amount of power required for an application is the
larger of two values:
1. Warm-up power + Heat lost during warm-up
2. Process heat + Heat lost in steady state
Warm-up power: Watts required to bring an object to
temperature in a given time. The basic formula is:
where:
m = Mass of object (g)
C
p
= Specific heat of material (J/g/°C)
T
f
= Final temperature of object (°C)
T
i
= Initial temperature of object (°C)
t = Warm-up time (seconds)
For other materials see Minco white paper “Prototyping
Techniques for Etched-Foil Heate
rs” at www.minco.com
To get: Multiply:
J/g/°C BTU/lb/°F × 4.19
g/cm³ lbs/ft³ × 0.016
Process heat: Heat required to process a material when the
heater is performing useful work. The formula above also
applies here, but must also include latent heat if material
changes state (melts or evaporates).
Heat loss: All systems lose heat through convection (air or
liquid movement), conduction through support structures,
and thermal radiation.
White Papers
Download these helpful white papers to assist in designing and
testing with Thermofoil heaters:
• Estimating Power Requirements for Etched-Foil Heaters
• Prototyping Techniques for Etched-Foil Heaters
()
()
t
TTmC
wattsP
ifp
−
=
Material Specific heat (J/g/°C) Density (g/cm³)
Air 1.00 0.0012
Aluminum 0.88 2.71
Copper 0.38 8.97
Glass 0.75 2.64
Oil (typical) 1.90 0.90
Plastic (typical) 1.25 Varies
Silicon 0.71 2.32
Solder 0.19 8.65
Steel 0.50 7.85
Water 4.19 1.00
INNER ELEMENT
POWER SUPPLY
OUTER ELEMENT
POWER SUPPLY
Conducting experiments
Heat transfer theory is complex. It’s usually best to prot
otype
your system with actual heaters to observe behavior and fine-
tune the design. Minco offers a variety of tools to help you:
Design Kit: The Flexible Heaters Prototype Design Kit
(part number TB-H1) allows you to easily test and prototype
a heating concept before starting on a journey of custom-built-
to-order product.
Filled with flexible Thermofoil heaters, instructions and
technical data, this kit will help you move towards successfully
integrating flexible heaters into your application. Learn more at
www.minco.com
V
ariable power source: An AC power supply (“Variac”), power
resistor, or rheostat lets you test different power levels across
the heater or zone by zone.
Temperature sensor(s): A small Thermal-Ribbon RTD such as
model S665 is easy to move and reapply to test temperature in
various locations. See sensor options in the "Sensors,
Controllers & Accessories" section.
Controller: Models CT325, CT15, and CT16A cover the range
from simple to sophisticated design for testing control
schemes. See controller options in the "Sensors, Controllers &
Accessories" section.
A mosaic of standard heaters, with dual power supplies, helps
to determine edge profiling for uniform temperature.
The resulting custom heater looks like this.