Last updated on January 16th, 2024 at 07:44 pm

Boiler heaters have serviced various facilities for well over a century. As reliable as they can be, it’s important to remember that not all boilers are made equal, and it’s essential to test a boiler’s efficiency. That is especially important when using boilers for specific industrial purposes. This post will examine how industrialists can determine the efficiency of a boiler heater. 

Design factors 

The design of a boiler heater plays an essential role in its efficiency. That refers not to aesthetics, of course, but to the physical configurations that govern how the heater delivers and circulates heat. Managers of an industrial application must consider these designs since they can enhance or diminish the outcome of their processes. 

Boiler heating surface

Measured in square feet per boiler horsepower, the heating surface of the boiler details how hard the vessel is working. Although this is a performance attribute, it’s a design element because this measurement is determined by the circulation design incorporated by the manufacturer. 

For example, it’s standard for manufacturers to use designs that provide five square feet per boiler horsepower. Thanks to improved heat transfer tubes, boilers require less output power, making them more efficient. Of course, the output your boiler needs can be customized for your application. 

The number of boiler passes 

The number of boiler passes refers to the amount of times hot gas travels through a boiler. For example, four boiler passes allow hot gasses to exchange heat in the water in the boiler. The number of passes a boiler has does influence its efficiency, but more (or less) is not better. 

What matters is whether the number of passes produces efficient heat with minimal waste for the application. With that said, improved tube design has made it possible to double the heat transfer rate of boiler passes. 

Calculations to determine the efficiency

The most effective means of determining a boiler’s efficiency is to calculate what’s known as efficiency calculations. They are industry-accepted standards that help identify whether a boiler is efficient enough, and include a wide range of factors involving temperature, energy wastage, and more. 

Efficiency calculations for boiler heaters

• Flue gas temperature: This refers to the temperature of combustion gas as they exit the boilers. Specific flue temperatures can indicate whether the boiler is working efficiently or not.   
• Stack Losses: A measure of heat carried away by moisture loss and dry flue gas. Generally, the lower the stack temperature is, the more efficiently the boiler works. 
• Heating medium temperatures: Typically, when the heating medium is cooler, the more efficiently the boiler works. 
• Radiation and convection losses: In many cases, losses of heat in either form can signal a boiler that’s not working at maximum efficiency. However, this isn’t set in stone since losses are expected under certain conditions (i.e., a boiler placed outside). 
• Excess air: Excess air supplied to a burner means greater energy consumption and translates to lower efficiency. However, seasonal temperatures and barometric pressures can influence air flows. 
• Ambient air temperature: Ambient temperatures refer to the air temperature surrounding the boiler. Boilers are designed to be warm, but certain environments can reduce their efficiency if ambient temperatures are too low (i.e., being outside).
• Turndown: This refers to the ability of a boiler to achieve a wide range of output, from high to low temperatures. Usually, high turndowns indicate greater efficiency. 
• Fuel specification: When speaking of fuel specification, we’re referring to the type of fuel the boiler uses and its effect on the boiler’s efficiency. For example, fossil fuels fire more efficiently than natural gas because there’s reduced water vapour loss with fossil fuels.

Combustion efficiency

Combustion efficiency refers to the boiler’s ability to burn fuel and absorb the heat it generates. To determine efficiency from this standpoint, operators measure the amount of unburned fuel and excess air in the exhaust. 

Generally, boilers are considered efficient if they boast low levels of unburned fuel and low excess air levels. Boilers that only operate at excess air levels of 15 percent or less are considered more efficient. When they run at these levels, they use less heat from the combustion process to heat excess air.  It’s important to note that combustion efficiency can and often does vary depending on the fuel that’s being burned. 

Air/fuel efficiency

Another way to determine the efficiency of industrial boiler heaters is to measure air/fuel efficiency—that either constitutes fuel-to-steam or fuel-to-water efficiency. The purpose of measuring this is to determine how much radiation and convection losses are occuring in the boiler. There are two ways to measure this efficiency:the input-output method and the heat loss method. 

Input-output method

With the input-output method, the goal is to determine efficiency based on the output-to-input ratio of the boiler. To calculate it, you must divide the boiler’s output by its input (both in BTUs) and multiplying it by 100. It usually requires instrumentation to determine the output and input of the boiler. 

Heat loss method

With the heat loss method, you determine a boiler heater’s efficiency by measuring its heat losses. To take this measurement, you subtract 100 percent of the total percentage of either stack, radiation, and convection losses. The remaining figure accounts for the boiler’s fuel-to-steam efficiency. 

Choosing efficient boiler heaters from the get go

Measuring boiler efficiency is crucial when you have an existing unit, and need to decide whether it’s time to repair or replace it. Determining this efficiency will help you make decisions that can make your heating applications more cost efficient. 

However, as boiler heater technology improves, so does efficiency. The components of industrial boiler heaters can now produce high levels of heat using less energy, making them more efficient than their predecessors. 

Here at Wattco, we offer a selection of boiler heater options that can meet your industrial heating needs without sacrificing efficiency. We can build custom solutions to meet the demands of your industry, especially if pre-built models don’t suffice. 

Get a quote for your industrial boiler heater today. Our representatives will help you find the exact setup needed for your industrial needs.