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Introduction to Flexible Heaters
What is a flexible heater?
Fibre optics are essentially light pipes. The group of sensors known as fibre optic thermometers generally refer to those devices measuring higher temperatures wherein blackbody radiation physics are utilised. Lower temperature targets, say from -100°C to 400°C can be measured by activating various sensing materials such as phosphors, semiconductors or liquid crystals with fibre optic links offering the environmental and remoteness advantages.
Important Formula's To Know
Ohms's Law
Ohm's law shows the relationship between voltage, wattage, amperage, and resistance. It is important to know Ohm's law in order to calculate the load you will be switching with your thermostat or digital controller. For example if you select a flexible heater which is rated 200 Watts and apply 120 Vac, the current will be 1.6 Amps
A is equal to W / V where: A = Amperes; W = Wattage; V = Voltage
Using our example above 200 Watts / 120 Vac = 1.6 Amps.
Some other variation of Ohm's Law:
| Volts |
= |
Watts / Amperes |
| Volts |
= |
Amperes x OHMS |
| OHMS |
= |
Volts / Amperes |
| Amperes |
= |
Volts / OHMS |
| Watts |
= |
Volts x Amperes |
|
Killowatt Requirement
To determine the kW required to be heat up a solid. The following formula is used.
kW = (WT x Cpx Δ T)/3412 x h
Where:
| WT |
= |
Weight of Material, lbs |
| Cp |
= |
Specific Heat, BTU/lb-°F |
| Δ T |
= |
Temperature Rise, °F |
| 3412 |
= |
Conversion Factor, BTU/kWh |
| g |
= |
Heat-up Time, hrs |
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Flexible Heater Selection
The key questions which need to be answered before selecting a flexible heater are:
- How much wattage is required?
- What voltage will be used?
- If it is a flat surface, what size will be needed?
- How long do the heater leads need to be?
- Will you require a thermostat or a digital controller with sensor?
- What is maximum temperature?<
- For flat surfaces will require wire wound or etch foil?
- What is the time required to reach your temperature?<
- What is the ambient temperature?
- Is insulation being used?
Temperature Controllers and Sensors for Flexible Heaters
There are a variety of temperature controllers and sensors one can use depending on the application. One of the more popular sensor types for flexible heater applications are the surface mount temperature sensors. Thermocouple, RTD or Thermistors are available with an adhesive backing or the ability to be cemented to the surface being heated. There also bolt on and magnetic surface mount type temperature sensors available. Digital temperature controllers come in many different sizes with many output and input choices. Thermcouple and RTD inputs are the most popular with a mechanical relay or dc pulse output. DC pulse ouputs allow the user to go to a larger relay to switch the heater load. Thermostats are also available for the most basic applications.
Here is a typical combination of products:
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Flexible Heater Types
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OMEGALUX® silicone rubber fiberglass insulated flexible heaters can improve heat transfer and speed warm-ups w here controlled heating is required in confined areas. All heaters where both the length and the width dimensions exceed 12" (305 mm) use the wire-wound element design. Effect of power density: gentle warming is best done with 2.5 W/in2. A good all purpose unit is the 5 W/in2. Rapid warm-up and high temperature are achieved with the 10 W/in2; however, temperature must be controlled as the safe maximum operating temperature limit of 450°F (232°C) may be exceeded.
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Kapton insulated heaters are available in a variety of shapes, sizes, and wattages. Wattage ratings are 2.5, 5, or 10W/in2 at 115 or 28 V. Kapton offers a high degree of resistance to chemicals, and has excellent outgasing properties in high vacuum environments. Typical construction consists of an etched foil element of 0.0005" or 0.0001" thickness which is encapsulated between two layers of 0.002" Kapton and 0.001" FEP adhesive.
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OMEGALUX® Silicone Rubber Extruded Heating Tapes are lowwatt density electrical resistance heaters designed for temperature maintenance in applications requiring moisture and chemical resistance. Silicone rubber tapes are constructed of finely stranded resistance wires fully insulated with braided fiberglass and knitted into flat tape with fiberglass yarn. These tapes are encapsulated in a voidfree silicone rubber sheath.
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OMEGALUX® rope heaters apply heat to tubing with diameters as small as 1/8" (3.2 mm). Featuring a maximum allowable operating temperature of 482°C (900°F), the FGR series rope heaters can be wrapped around either conductive or non-conductive surfaces. Each end terminates with 24" (610 mm) long fiberglass insulated lead wire. These rope heaters are very similar to our heater tapes. Please review our tape heaters for your application needs.
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The OMEGA® TOTE Series tote tank heaters are flexible wraparound surface heaters offered in different sizes based on height. These heaters provide a quick, easy, non-invasive way to warm your product. They fit nearly every standard tote tank utilizing adjustable nylon straps with buckles. There are 3 straps for placing around the tank and 2 for across the top. Units include an adjustable thermostat and a manual reset high-limit thermostat for each of the 2 zones.
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OMEGA's GCW Series gas cylinder warmers create a convection current and increase pressure inside the cylinder. This cost-effective process reduces condensation, allowing more gas to fill the cylinder. Use with gases such as SF6, propane, nitrogen, oxygen, BCl3, WF6, and HF.
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