In today's modern world, energy efficiency has become a top priority for many industries. One area where significant strides have been made is in refrigeration technology. Flexible heaters have emerged as an innovative solution that has revolutionized refrigeration efficiency.
This blog post will explore how flexible heaters work, what their benefits are, and the various applications used within the refrigeration industry.
Understanding Flexible Heaters
Flexible heaters are thin, lightweight heating elements that can be bent and shaped to conform to various surfaces. They typically consist of a resistive element, such as a wire or a conductive ink, sandwiched between layers of insulating material, like silicone or polyimide. Flexible heaters can be customized in size and shape to meet the unique requirements of different applications.
They can be easily shaped and molded to fit various surfaces and applications and are commonly made of materials that offer excellent flexibility and thermal conductivity, they can be designed to operate at various voltages and wattages, making them suitable for a wide range of applications, including refrigeration.
In refrigeration applications, flexible heaters are typically used to prevent the formation of ice on evaporator coils. When the temperature in a refrigeration unit drops below freezing, moisture in the air can condense and freeze on the evaporator coils, reducing their efficiency and potentially damaging the unit. By placing a flexible heater on the surface of the evaporator coils, the heater can provide a steady source of heat that prevents ice from forming. This allows the refrigeration unit to operate more efficiently and helps to extend the lifespan of the unit. Additionally, flexible heaters can be used to heat up the compressor and other components of the refrigeration system, ensuring that they operate at the proper temperature and reducing the risk of damage or failure.
The refrigeration process offers many opportunities to explore where flexible heaters can be considered for use, to improve efficiency, design, and cost.
Condensation Prevention
It’s a basic fact that humidity will condense on the coldest surfaces. Perhaps you have seen this in your bathroom, after a hot shower, when condensation appears on the windows and mirrors and runs down. A similar effect occurs in a refrigerator.
Condensation occurs when moisture in the air comes into contact with a surface that is colder than the dew point temperature. To prevent condensation from forming on the surface of the flexible heater, the heater should be insulated with a material that has a low thermal conductivity, such as closed-cell foam or fiberglass. Additionally, a vapor barrier should be used to prevent moisture from entering the insulation layer. The temperature of the heater should be maintained above the dew point temperature to prevent condensation from forming on its surface.
Enhancing walk-in freezer efficiency with state-of-the-art flexible heaters ensures optimal temperature control and energy conservation.
So, when an appliance door is opened, warm outside air meets cold interior air and condensation can form on the door seal. Keeping the door seal at ambient temperature will help prevent this. Flexible heaters can be mounted to door gaskets to provide a constant thermal output and prevent condensation and ensuing mildew and mold. The overall thin dimensions of the flexible heaters will allow for a tight fit and a continued secure seal, by the gasket. The high traffic flow of a reach-in refrigerator/freezer unit, or a walk-in refrigerator/freezer unit, in the food service field, would be a prime candidate for condensation control.
Temperature Control
In single-circuit appliances and appliances with a 4-star freezer compartment, temperatures are usually regulated according to refrigeration compartment temperature. When ambient temperatures fall, an issue arises because the refrigeration compartment will not need to be cooled regularly and this means that the associated 4-star freezer compartment can then become too cold. In such cases, the refrigeration compartment is artificially heated by a light bulb or an electrical heater to force the refrigerator to cool down more frequently and thus keep the 4-star freezer compartment sufficiently cool.
To address this issue, the refrigeration compartment may need to be artificially heated using a light bulb or an electrical heater to prompt the refrigerator to cool down more frequently and maintain suitable temperatures in the freezer compartment. Flexible heaters can be a helpful solution for this problem, as they can be mounted with a temperature control thermistor to assist with maintaining freezer efficiency. This can provide more precise temperature control and ensure that the 4-star freezer compartment remains at an appropriate temperature.
Evaporation of Condensation
The compressor’s crankcase lubricant, or oil, has many important functions. Even though the refrigerant is the working fluid required for cooling, oil is needed to lubricate the compressor’s moving mechanical parts. Under normal conditions, there will always be a small amount of oil that escapes a compressor’s crankcase and circulates with the refrigerant throughout the system. The proper refrigerant velocity traveling through the system’s tubing will return this escaped oil to the crankcase over time, and it is for this reason that oil and refrigerant must be soluble in one another.
Integrating flexible heaters in refrigeration systems helps to prevent refrigerant migration and ensures the longevity of mechanical components.
At the same time, however, the solubility of the oil and refrigerant can cause another system problem. That problem is refrigerant migration. Flexible heaters can be designed to help combat refrigerant migration. The function of the heater is to hold the oil in the compressor’s crankcase at a temperature higher than the coldest part of the system. The heater dimensions allow for application in tight-fit areas, and their resistance to oils and chemistries makes them ideal candidates for this purpose.
Defrosting the Evaporator
Electric defrost is a relatively simple method for defrosting in applications where off-cycle is not practical. Electricity is applied, heat is created and the frost melts from the evaporator. Electric defrost solutions, using flexible heaters, provide a more positive defrost than off-cycle defrost, with shorter durations. Once again, the defrost cycle will terminate on time or temperature, which can be controlled with an applied thermistor to the flexible heater.
Upon defrost termination there may be a drip downtime; a short period that will allow the melted frost to drip off the evaporator surface and into the drain pan. In addition, the evaporator fan motors will be delayed from restarting for a short amount of time after the refrigeration cycle commences. This is to ensure that any moisture still present on the evaporator surface will not be blown into the refrigerated space. Instead, it will freeze and remain on the evaporator surface. The fan delay also minimizes the amount of warm air that is circulated into the refrigerated space after the defrost terminates. Fan delay can be accomplished using the same thermistor controls on the flexible heater. The use of flexible heaters can eliminate the weight and costs of conventional rod heaters.
Process Icing Concerns
Every refrigeration design is subjugated to a possible icing concern that will not be evident in initial engineering and prototyping. When quality and operational issues arise due to an icing condition, instead of a costly redesign, look toward flexible heaters as a thermal solution. With the ability to be highly customized, flexible heaters can be designed to accommodate the tightest spaces and the most intricate designs. With multiple mounting methods and resistance to most solutions and chemistries, flexible heaters are key to solving your icing problems. Add to that the low watt densities required to prevent icing, and the operating life will be greatly extended, offering a long-term cost resolution to an inherent refrigeration design.
Summary
Flexible heaters have revolutionized refrigeration efficiency by offering solutions to various challenges faced by refrigeration systems. They can be easily shaped and molded to fit various surfaces and applications, and their flexibility and thermal conductivity make them ideal for refrigeration systems. They can be used to prevent the formation of ice on evaporator coils, heat the compressor and other components of the refrigeration system, prevent condensation, help combat refrigerant migration, and defrost the evaporator.
By utilizing flexible heaters in refrigeration systems, one can significantly increase efficiency, reduce energy consumption, and extend the lifespan of the refrigeration unit. The opportunities to explore the use of flexible heaters in refrigeration processes are endless, and it's time to embrace them to achieve energy efficiency and environmental sustainability.
If you'd like to find out more information about how flexible heaters can help with your project, contact the team at Epec today.
