Key Questions to Ask When Ordering Forced Draft Type Evaporative Condenser

Refrigeration is an essential process in many industrial and domestic environments, and the proper functioning of its components is crucial for efficient operation. One such component is the condenser, particularly the “forced draft air-cooled condenser.”

If you want to learn more, please visit our website CHT TECK.

What is the condensation of refrigerant?

Condensation is a phase in the refrigeration cycle where the refrigerant, after absorbing heat from the environment to be cooled, changes from a gaseous to a liquid state. This state change releases heat, which is expelled outside, allowing the refrigerant to continue its cycle. At this stage of the process, the condenser plays a role.

Types of Condensers

Air Forced Condenser:

• Tube and Fin Design: Consists of tubes carrying the refrigerant, surrounded by metal fins that facilitate heat dissipation. A fan typically forces air through the fins to improve heat transfer efficiency.
• Application: Most common in commercial refrigeration due to their simplicity and cost-effectiveness. However, they require adequate airflow and space for the expulsion of hot air.

Water Condenser:

• Tube-in-Tube or Shell and Tube Design: The refrigerant flows through one set of tubes while water flows in the opposite direction through another set or around the tubes, depending on the design.
• Application: Used in areas with abundant water supply and where the cost of using water is lower than the cost associated with heat dissipation to air. Often require a water treatment system to prevent scale formation in the tubes.

Evaporative Condenser:

• Design: A combination of an air and water condenser. The refrigerant condenses in coils or tubes while water is sprayed over them. Simultaneously, an airflow is introduced, causing some of the sprayed water to evaporate, removing heat in the process.
• Application: More efficient than pure air condensers, especially in warm climates. However, they require a water supply and regular maintenance due to potential issues like water quality and algae growth.

Static Condenser:

• Design: Typically feature a parallel plate design. Composed of two conductive plates, usually metal, separated by a dielectric (insulating) material. This design maximizes the charge storage capacity. The efficiency and capacity of the condenser depend on the surface area of the plates, the distance between them, and the type of dielectric material used.
• Application: For example, in domestic refrigerators, where it helps convert the hot, high-pressure refrigerant gas exiting the compressor into a cooler liquid. By releasing the refrigerant’s heat to the environment, the condenser allows the cooled liquid to return to the compressor to continue the refrigeration cycle, thus ensuring efficient and consistent operation of the appliance.

Forced Draft Condenser: Functioning and Typology

The forced draft condenser, also known as “air forced condenser” or “air cooled condenser,” uses fans to force air circulation through the internally placed battery, consisting of a coiled tube, usually copper, and fins, most often aluminum. This airflow helps dissipate the heat from the refrigerant, facilitating its condensation. Since the efficiency of condensation is directly related to how quickly heat can be removed, the ability to force air movement is essential for effective cooling.

Different types of forced draft condensers used in commercial refrigeration include:

• Single fan condensers: Designed for basic operations and are very common in small to medium systems.

• Flat condensers: Their design optimizes thermal exchange and are often preferred for limited spaces and use in integrated groups.
• Dual fan condensers: Ideal for larger systems, as they have a larger exchange surface and, therefore, greater cooling capacity.

The relationship between the compressor and the condenser

The compressor is another crucial element in the refrigeration circuit. Its main function is to compress the gaseous refrigerant and indirectly raise its temperature. Once the refrigerant exits the compressor, it enters the condenser in a gaseous and high-temperature state. The condenser, with the help of forced airflow, dissipates this heat, and the refrigerant condenses, turning back into a liquid.

In summary, the “forced draft condenser” plays a vital role in the refrigeration circuit. Working in conjunction with the compressor, it ensures that the refrigerant circulates properly, thus maintaining the system in optimal operating conditions. It is essential to select the right type of condenser according to specific needs to ensure maximum system efficiency.

Fans in forced draft condensers: specifications and leading brands

In forced draft condensers, the fan is an essential component, responsible for forcing air circulation through the heat exchange batteries to dissipate heat. When selecting a suitable fan, several specifications must be considered:

Speed:

It’s crucial that the fan can operate at different speeds, allowing for airflow adjustment according to system demands. A typical rotation speed can range from 850 to rpm, depending on the size and application of the condenser.

Noise generation:

In residential or commercial areas, the noise level generated by the fan mustn’t be bothersome. Typically, they are expected not to exceed 50-60 decibels at full load, although this can vary according to local regulations and specific applications.

Number of blades:

Un mayor número de alas puede proporcionar un flujo de aire más uniforme y eficiente. Los ventiladores suelen tener entre 3 y 6 alas, dependiendo del diseño y la función deseada.

Dimensions:

These must be compatible with the size of the condenser and the available space. It’s essential to ensure that the fan adequately covers the coil area for efficient heat dissipation.

Regarding the most relevant brands in the manufacturing of fans for forced draft condensers, companies like Ebm-Papst or S&P stand out. These companies are known for offering high-quality, durable, and efficient solutions for refrigeration systems.

When choosing a fan, it’s vital to ensure it meets the necessary specifications for the system and local regulations, thus guaranteeing optimal and safe operation of the forced draft condenser.

Regardless of the season, maintaining good water quality will impact the equipment operation and useful life. Sunlight can promote the growth of bacteria.

Equipment that reduces the amount of light entering the condenser will reduce water treatment cost and, therefore, annual operating expenses. Induced-draft models are built with basins open to the atmosphere. Steps must be taken in the louver design to reduce the amount of light entering the basin, as well as keeping debris out and water in.

Ambient Conditions, Maintenance, and Materials

Ambient conditions affect the selection of an evaporative condenser. The design wetbulb temperature has a significant impact on the size of the evaporative condenser.

The location of the equipment will determine the design wetbulb temperature for the condenser selection. ASHRAE and other organizations (such as the National Weather Service) publish data including design wetbulb temperatures for each municipality.

In addition, the water quality, maintenance history, and environment will impact the condenser selection as well as the materials of construction required for each application. For example, if the condenser is installed in a location where it will be difficult to replace or is subjected to aggressive water chemistry, then it should be built using materials such as stainless steel for longer product life and resistance to corrosion.

The materials of construction also affect product selection. The major manufacturers build evaporative condensers from hot dip galvanized steel. The heat exchanger coil, the heart of the evaporative condenser, is built from carbon steel and the entire assembly is hot dip galvanized after fabrication.

The rest of the condenser is typically galvanized steel — either hot dip galvanized after fabrication or mill galvanized. Specific components, such as the water distribution system or air inlet louvers, are most often made from PVC.

Alternate materials of construction, such as stainless steel, are available at additional cost. Specific areas of the condenser may be built from different materials; for example, the basin only may be constructed from stainless steel.

Each option will add to the cost differently for different types of condensers. Each manufacturer will provide an increase in cost for alternate materials of construction, and this cost will then determine the condenser selection.

Operating Requirments

System operation can influence the condenser selection. If the condenser load fluctuates, then the condenser should have multiple fan motors and be able to cycle off the individual fan motors to match off-peak loads.

Alternately, the lower the condensing pressure, the less compressor horsepower is required to maintain a given heat load. Therefore, operating the condenser at full capacity during off-peak loads or during periods of low wetbulb temperatures reduces the system head pressure, which can be beneficial to the total system efficiency.

If you want to learn more, please visit our website Forced Draft Type Evaporative Condenser.

In fact, compressor horsepower can be reduced 1% to 2% for every 1°F drop in condensing temperature. The wetbulb and pressure requirements for expansion valves are limiting factors in reducing the condensing temperature.

Another method in reducing head pressure and subsequently reduce operating cost is to increase the capacity of the evaporative condenser. Once a given plan area is established for an evaporative condenser, the impact of increasing the capacity within the same plan area is minimal. The additional capacity can be used to reduced the head pressure or for future additional system load.

Future system loads or expansion must also be considered when sizing an evaporative condenser. A short-term benefit of a condenser sized for the future load is reduced operating costs due to lower head pressure.

Sizing and Selection

In sizing evaporative condensers, the first step is to determine the heat load. Often expressed in “tons of refrigeration,” it represents the heat requirement of the refrigeration system.

A ton is a unit of refrigeration capacity represented by the amount of heat required to freeze 2,000 lb of ice in a 24-hr period. This is equal to a heat rate of 12,000 Btu/hour (Btuh).

In order to use the same “tons” as evaporator tons, condenser manufacturers typically use 14,700 Btuh/ton to approximate the heat introduced to the refrigerant by the compressor. It is more accurate and less confusing to discuss heat load solely in evaporator tons or in Btuh.

Additional terms used in condenser selections are “nominal tons” and “corrected tons.” The term nominal tons should be given to the actual heat load for a refrigeration system. During the selection process, the nominal tons are adjusted to reflect the system operating conditions of suction temperature, condensing temperature, and wetbulb temperature, and relate these conditions to the base conditions on which the condenser is rated.

When making a condenser selection, the refrigeration system dictates several important requirements of the condenser. The evaporator load determines the amount of heat to be rejected to the atmosphere by the condenser. The compressor will determine the condensing temperature. The ambient wetbulb temperature also affects this temperature.

The condensing temperature can never be lower than the wetbulb temperature. The relationship between the condensing temperature and wetbulb temperature is the major driving force in condenser size. The closer the condensing temperature is to the wetbulb, the larger the evaporative condenser. Conversely, the higher the condensing temperature, the smaller the condenser, but with the penalty of increased energy consumption due to higher compressor horsepower.

Selection Methods

Most manufacturers use two selection methods: the heat-of-rejection method and the evaporator tons method.

As discussed earlier, condensers are rated for a given set of conditions. For ammonia, the base rating is for 20° suction temperature, 96.3° condensing temperature and 78° wetbulb temperature for ammonia (R-717).

The heat-of-rejection method uses the actual heat load on the condenser calculated by adding the evaporator load in Btuh and the compressor heat in Btuh. The heat load is multiplied by a factor load based on the relationship of condensing temperature and entering air wetbulb to calculate the corrected heat load. The corrected heat load is then used to determine the unit selection.

The evaporator tons method multiplies the evaporator load times factors for suction temperature and for the relationship between the condensing temperature and entering air wetbulb to calculate the corrected tons. The corrected tons are then used to determine unit selection.

The evaporator tons method relies on an estimation of compressor heat based on a factor tied to the system suction temperature using open-type reciprocating compressors. The actual compressor heat will vary with the type of compressor and manufacturer.

Conclusion

Identifying the most important factors such as cost, physical size, operating costs, sound ratings, and equipment features that pertain to the specific project will indicate the type of condenser as well as provide the best equipment selection.

The choices for each customer may vary based on energy efficiency as well as capacity in a given plan area.

Making the right choices will ensure that the right product is used for the right application.

Kollasch is product manager of evaporative condensers for Evapco. For more information, contact the company at P. O. Box , Westminster, MD; 410-756-.

Sidebar: Installation Tips

Evaporative condensers require an abundance of fresh air to accomplish their designed function. The availability of that air and the efficiency of its use are prime concerns when installing an evaporative condenser.

A condenser, which uses less air, will likely have an advantage in a well enclosure. If there are existing units on site or future expansions planned, then the location of the condenser and the availability of fresh air becomes critical. Even prevailing winds and piping can affect condenser performance by affecting the airflow.

The key to a good installation is to have unaffected airflow to the air intake of the condenser and no restriction on the discharge. The condenser may require special support to provide free access of air to the unit.

In the event that the airflow is somehow affected by, for example, the building next to the unit or by the prevailing winds, then the discharge air can be directed back toward the air intake and recirculation will occur.

Recirculation of the discharge air can reduce condenser performance significantly. A 2°F increase in the wetbulb temperature will reduce performance by 16%. A 5° to 6° elevation in wetbulb can reduce capacity by 50%. Minimum clearance recommendations should be followed to provide sufficient fresh air for proper operation. Clearances around condensers are different for each type of condenser.

Forced-draft models require the most clearance in front of the fans while air enters on all four sides on most induced-draft models creating clearance requirements for airflow on each side. The site determines how much space is available and the size of the condenser will then determine the equipment selection.

For example, if a condenser were to be installed near the property line, then an induced-draft unit would be preferable, or a forced-draft unit rotated so the fans were facing away from the neighbors.

If the condenser were next to a taller office or apartment building, a forced-draft unit would be preferred to again direct the sound away from the neighbor. If the condenser were to be installed in a well enclosure, then the system engineer would choose between installing a forced-draft unit against one of the walls, or placing an induced-draft model in the center of the well.

The company is the world’s best Forced Draft Evaporative Condenser supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.