Boilers vs. Direct-Fire vs. Glycol: Water Heating Systems to ...

As explained in this previous post, food processing operations require substantial energy. While utility costs are unavoidable, various factors can enhance efficiency and achieve long-term cost savings, including a facility&#;s water heating system. Considering your production specifications and overall environment, there are specific systems available that can effectively minimize energy consumption in your food or beverage production. Thus, it&#;s important to explore these systems and understand their differences. So, what are these systems, and how do they vary from one another?

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Boilers

Boilers heat water indirectly by using a heat source to produce steam or hot water that circulates through a network of pipes or radiators. They are fueled by natural gas, oil, coal or biomass. Boilers also have diverse food and beverage production applications, making them one of the industry&#;s most commonly used heating systems.

In manufacturing settings, the hot water distribution from the boiler to different use points may result in heat loss through piping systems. Insulation and design considerations can help minimize that heat loss, however. Another option is adding an economizer, which captures waste heat from the boiler and sends it through a heat exchanger. This energy is then reused in other production processes, like clean-in-place (CIP) systems, at the plant.  

Direct-fired water heaters

As its name implies, a direct-fired water heater directly heats the water using a burner or heating element. The heat source, such as natural gas, propane or electricity, is applied directly to the water via a burner or heating element typically located inside the water tank or chamber. Direct-fired systems tend to have very high energy efficiency because they heat the water directly, minimizing heat loss by design. They provide hot water on-demand with faster heat-up and response times. This can benefit manufacturing settings where various processes or equipment require a continuous hot water supply. Combustion byproducts result from the fuel burning of these systems, so adequate ventilation and safety measures must be in place to ensure a safe working environment.

Glycol heating systems

Glycol water heating systems utilize a mixture of water and glycol as the heat transfer fluid. A glycol-water solution is circulated through a closed-loop system comprised of a water heater or boiler, piping, pumps and heat emitters (e.g., radiators, fan coils or heat exchangers). The solution transfers heat from the water heater or boiler to the heat emitters. In those emitters, the heat is transferred to the surrounding water or other medium to provide warmth or maintain desired temperatures.

Glycol heating systems are commonly used in applications that need to prevent freezing or maintain consistent temperatures in the water distribution system, often in cold climates or environments where water may be exposed to low temperatures. Glycol heating methods can also utilize wasted energy by harnessing the heat generated from ammonia compressors used in refrigeration. This waste heat can be efficiently circulated through an underfloor system in freezers, preventing frost heave (using residual heat and glycol).

Considerations for these heating systems include potential glycol degradation, regular glycol concentration testing and maintenance, and ensuring proper ventilation and safety measures to address possible gas release during high temperatures or combustion.

Adding a heat pump

Heat pumps find widespread usage in HVAC systems, and they are additionally employed on the discharge side of refrigeration systems to provide assistance in water heating. This process involves sending heat to the rooftop condenser to keep the system operational. Subsequently, the discharge gas is intercepted, and a heat exchanger is installed in front of the condenser to aid in both water condensation and heating. Implementing this technology requires a significant upfront effort and is often easier to incorporate into new construction projects rather than retrofitting existing systems.

Pros and cons

Boilers are versatile, generating hot water and steam for various applications in food and beverage plants. Direct-fired heaters provide more precise temperature control, while glycol systems offer an even broader temperature range, operating at higher temperatures than steam with lower pressures and eliminating the need for a dedicated boiler attendant. Boilers can also improve efficiency through various enhancements such as heat reuse and insulation.

In general, direct-fired systems have a smaller footprint and achieve and maintain target temperatures more quickly. Both direct-fired and glycol systems can be more energy-efficient but only in specific applications, which can limit large-scale operations. While water is cheaper, glycol&#;s superior heat transfer makes it highly efficient. Glycol&#;s stability also prevents chemical degradation that could lead to system corrosion or component fouling, avoiding costly repairs or replacements.

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Designing, installing or commissioning any system requires a precise and accurate approach from the very beginning. Stellar offers a comprehensive range of solutions, regardless of the project size, providing a single source for all your needs from initial conception to project commissioning and beyond.

Have questions about energy conservation strategies for your plant? us at  or give us a call at 800.488..

HEAT is an industry expert with more than 100-years combined experience designing water & glycol heat transfer systems&#;our Sales Engineers will help you choose the water & glycol heating system that is best for you. Depending on your needs, one of our Pre-Engineered Systems could help meet your time sensitive demands, or a fully custom water & glycol system that incorporates the additional control and safety features your process requires will be the best solution. Custom designs can incorporate your available utilities (electric, natural gas, steam, central plant hot oil loops, etc.) and are offered at 4 different levels of our custom design process, all with a dedicated project manager.

Closed-Loop Water Heating System

At their core, Glycol Heating Systems work by circulating heated water or a water/glycol mixture through a closed-loop piping circuit. This circulating fluid allows for the transfer of energy from a source to a product or process (heating), and also sometimes for transferring that energy away (cooling).

Water & Glycol Heating systems give you precise control of temperatures in a batch or continuous process and can operate at temperatures higher than steam (up to 350°F in some designs) with lower pressures, meaning no boiler attendant is needed.

What is the best heat transfer media? 

Based on its physical properties, water is the best heat transfer media. However, water has limitations as it nears freezing or boiling.

An ethylene glycol or propylene glycol mixture will lower the freezing point and raise the boiling point of fluid inside a heat transfer system, but this also influences the fluid&#;s heat transfer properties.

The choice of whether to use water or a water-glycol mixture as the heat transfer fluid depends on your process and industry needs.  Contact our experts to learn more about what is best for you.

Are Water Glycol Heating Systems Safe? 

Safety is HEAT's highest priority: all our designs are built to exacting codes and standards. Piping connections are all-welded, flanged, or threaded and insulated with fiberglass, rubber, or non-wicking cellular glass insulation. Every system is rigorously tested during our Factory Acceptance Test process, which you can witness in person or virtually. Our Service and Aftermarket teams are dedicated to providing you with on-site equipment start-up assistance, training, troubleshooting, and spare parts support. We also offer preventative maintenance and fluid care help to keep your system running safely and at peak performance.

We divide our water & glycol heating system designs into categories based on the heat source. Learn more below!

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