When designing or optimizing industrial heating systems, understanding the factors that influence heat loss is crucial. Accurate heat loss calculations help determine the correct insulation, power output, and electric heater specifications for your process. By reducing inefficiencies and targeting key heat loss factors, you can significantly improve energy efficiency and reduce operational costs.
In this guide, we’ll explore common contributors to heat loss and show how you can use Watlow’s process heating tools and engineering tools - heat loss factors to optimize your thermal system.
What Is Heat Loss?
Heat loss refers to the transfer of thermal energy away from your heater or heated product. This can occur in three primary ways:
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Conduction: Direct contact between materials, such as a heated surface and metal component.
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Convection: Heat transfer through air barriers around pipes, heaters, or enclosures.
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Radiation: Electromagnetic heat loss from uninsulated or exposed surfaces.
When using electric heaters, understanding how these forms of heat loss occur is critical for ensuring system efficiency.
Key Heat Loss Factors in Industrial Settings
Design engineers should consider the following when conducting heat loss calculations for any industrial heating system:
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Uninsulated surfaces (metal or non-metal)
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Vertical or horizontal insulated surfaces
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Water or liquid surfaces (oil, paraffin, etc.)
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Wind or air velocity (especially outdoors or ventilated spaces)
For example, an electric heater running through both oil and outdoor air must account for combined loss factors, such as conduction from the pipe surface, convection from surrounding air, and radiation from exposed components.
Why Managing Heat Loss Matters
Every watt of thermal energy lost is an inefficiency in your system. Reducing heat loss through insulation and optimal heater placement can:
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Lower your energy bills
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Improve process consistency
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Extend the lifespan of your electric heaters
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Allow for more accurate control using power and temperature controllers
If you move your production process or modify your system, revisit your heat loss calculations to ensure continued efficiency and performance.
Before choosing the right heating product, use a process heating tool to identify potential heat loss points. Calculating total heat loss allows you to:
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Choose the right size and power rating for your electric heater
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Determine whether a tubular, cartridge, or flexible heater is ideal
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Identify whether surface finishes or insulation changes are needed
Emissivity and Its Role in Heat Loss
Emissivity measures a material’s ability to emit infrared energy. High-emissivity surfaces (such as oxidized metal) emit more heat via radiation, while polished surfaces emit less.
Factors that affect emissivity:
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Heater surface finish (polished vs. oxidized)
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Thermocouple material
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Insulation type (metal vs. non-metal)
Using a more emissive material can either help or hinder your process, depending on the goal. Optimize emissivity when designing your system to reduce unnecessary heat loss.
How to Calculate Heat Loss Using Engineering Tools
Watlow provides advanced engineering tools - Heat Loss Factors to assist in accurate thermal design. Use the following methods:
Surface Orientation Adjustments
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Horizontal surfaces: Multiply the convection value by 1.29
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Vertical surfaces: Use the direct value
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Bottom surfaces: Multiply by 0.63
Emissivity-Based Guidelines
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For uninsulated surfaces (emissivity ~1.0), divide the temperature rise above ambient by 200.
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For insulated surfaces (1-inch insulation, K = 0.5 BTU-in/hr-ft²-°F), divide temperature rise by 950.
These formulas help estimate heat loss but should be adjusted using real emissivity values and insulation performance metrics.
Optimize Your Process with Watlow Heating Tools
Reducing heat loss doesn’t just lower energy usage — it also improves the quality and reliability of your thermal process. Watlow’s comprehensive suite of process heating tools, technical support, and high-performance electric heaters make it easy to design efficient, scalable systems.
Whether you’re upgrading PID controllers, evaluating new heaters, or refining your heat transfer setup, we offer the solutions you need.
Need Help with Heat Loss Calculations?
Use our engineering tools - Heat Loss Factors and interactive process heating tool to calculate and manage energy loss in your system. Contact Watlow for expert guidance on selecting the right electric heater and optimizing your thermal processes.
Factors that affect heat loss
Heat loss is the intentional or unintentional loss of thermal energy from a heat source to the material being heated. This can happen through conduction, convection and radiation. Conduction often occurs when an insulated or uninsulated component is in direct contact with another component. Convection occurs when your pipe, electric heater or other component has an air barrier around it. Radiation occurs when there is no contact and heat moves in electromagnetic waves.
At Watlow, we make sure you select the power and temperature controllers that best fit your heating application. One way to do this is to account for common heat loss factors. While every situation may have different factors that affect heat loss and heat transfer, here are some common areas that design engineers need to account for within the design of their thermal system:
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Uninsulated surfaces
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Vertical or horizontal insulated surfaces
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Water surfaces
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Oil or paraffin surfaces
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Wind velocity effects
These effects are cumulative, so an uninsulated pipe running partially through oil and partially through exposed outdoor air needs to include all three of these heat loss elements when making a calculation.
Heat loss is an inefficiency. Adjusting the temperature of your heater or protecting it from one or more of these heat loss factors can reduce the wattage usage of your system. This can save your facility a considerable amount in daily operating expenses.
Factors that influence heat loss can change when you relocate a process or make changes to your assembly line. Targeting the heat loss factors and making necessary adjustments with your controlling equipment or insulation strategies keeps your application operating at the same quality and consistency as it was before the change.
Calculating the heat loss of a system also helps you identify the correct heating product for a new line. Before deciding which type of electric heater to purchase, be sure to calculate all potential areas where heat loss can occur. These are crucial factors that will affect the size and type of heating product needed for your industrial process.
How emissivity affects heat loss
Emissivity is defined as the ability of a particular object or material to emit infrared energy. The emissivity factor of your heater, thermocouple and insulation type can also, therefore, affect the heat loss through radiation.
This is another piece of the puzzle when determining how much heat is needed for your specific application. Be sure to determine whether the heating surface would be more effective utilizing a polished surface or a more emissive medium or heavy oxide finish is needed. Even non-metals have emissivity factors, so checking on the impact of the insulation materials as well can result in less heat loss and better outcomes.
How to calculate heat loss factors
At Watlow, we offer a number of tools to assist you with calculating heat loss in your specific application. Multiply the convection curve value by a factor of 1.29 for horizontal heating products. Vertical heating should use the direct value of the curve. For bottom surfaces, multiply the curve by 0.63.
This calculation does not take into account all the heat loss factors that may affect your application. OEMs need a more accurate way to measure heat loss for their specific product, so alterations need to be made, called emissivity values.
Using this graph is helpful at high temperatures, but as the temperature reaches ambient, or 70 degrees Fahrenheit, it can be difficult to read. There are two general rules that can help you arrive at a more precise temperature reading:
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Calculate losses from an uninsulated surface with close to 1.0 emissivity by dividing the temperature rise above ambient by 200.
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Calculate losses from an insulated surface with an approximate thickness of one inch and K- value of 0.5 BT-in/hr-ft2-℉ by dividing the rise above ambient temperature by 950.
These calculations need to be adjusted based on emissivity and insulation rating of your product, but they can assist you in using the above graph more effectively.
How heat loss affects your industrial process
Heat loss factors not only help you adjust your power and temperature controllers but also find the ideal heater for your process. Browse our heating products to compare wattages, materials and other factors. Whether you are shopping for a new PID controller, heater or simply looking to improve the efficiency of your process, Watlow has the products and technical guides to help you understand and manage heat loss factors.