User Guide

Heat Transfer and Infrared Heater Basics
2 9-200.6
Types of Heat Transfer
Infrared heaters primarily transfer heat directly through
radiation. However, infrared heaters indirectly cause
conduction and convection heat transfer within a heating
application. The following is a summary of the different types
of heat transfer:
Radiation
This is the transmission of heat through a space by infrared
energy rays emitted from a hot surface. The infrared energy is
transmitted through space and heats only the objects the
energy strikes. The energy can actually pass through a
vacuum and remain virtually unchanged. A familiar example is
the Sun, which radiates energy to objects such as the Earth.
When a person is outside on a sunny day, the person feels the
warmth of the Sun. If a cloud passes over, the person feels
cooler. Although the air temperature doesn’t change, the
amount of radiant energy reaching that person is reduced
since the water droplets of the cloud absorbed some energy.
In the case of infrared heaters, the heat is radiated from the
heater to objects in the space such as storage racks,
machines, the floor, and people. These objects, in turn, radiate
the heat gained from the infrared heater.
Conduction
This is the transmission of heat through solid objects by the
exchange of energy from warmer molecules to cooler
molecules. An example is a pot on a stove. Even though the
flame does not directly heat the handle, it gets hot because
heat from the bottom of the pot is transferred to the cooler
handle.
In the case of the infrared heating application, the objects in
the space conduct heat gained through radiation from the
infrared heaters. For example, the warmed floor conducts heat
through the shoes of a person standing on the floor, warming
the person’s feet.
Convection
This is the transmission of heat through gases or liquids by the
movement of masses of the gases or liquids. An example is
air moving across a fin-tube heater. As the fin-tube element
heats the surrounding air, the air becomes less dense and
rises. Cooler air takes its place surrounding the heating
element and is heated. This process continues, heating the air
in the room.
In the case of the infrared heating application, the warmed
objects, such as the floor and storage racks, heat the air
surrounding the objects.
Types of Infrared Heaters
Modine offers two types of infrared heaters; high-intensity and
low-intensity. Both are certified for commercial and industrial
applications only. The following is a brief description of each
type of infrared heater:
High Intensity
Units utilize a diamond faced ceramic tile burner for maximum
heat transfer, housed in a rugged, aluminized steel frame. The
flame burns on the outer surface of the tile(s) with the infrared
energy efficiently directed by a polished aluminum reflector
mounted on the aluminized steel frame. Source temperatures
can range from 1800°F to 2200°F.
The units are certified for indoor use only and operate
unvented. A minimum positive air displacement of 4 CFM per
1000 Btu/hr input for natural gas or 5 CFM per 1000 Btu/hr
input for propane gas is required for proper ventilation.
Figure 2.1 – High Intensity Infrared Heater
Low Intensity
Low-intensity units utilize an aluminized steel heat exchanger
tube with a polished aluminum reflector that efficiently directs
infrared energy. The burner is mounted at one end opening of
the tube and exhausts at the other end opening. Tube
systems are available in either straight or U-tube
configurations. Source temperatures near the burner end of
the tube system can reach 1200°F.
Units are available as pressurized type systems, which provide
a power exhauster mounted at the same end as the burner to
force the products of combustion through the tube. The units
operate vented.
Units are for indoor or outdoor applications.
Figure 2.2 – Low Intensity Infrared Heater