Choosing the right chiller depends on a project’s specific application. Understanding how to size a chiller can provide you with the information you need to search for the best chiller to meet your needs.
It’s best to consult with a professional who has experience matching the right chillers to various applications, but knowing which chiller specifications you are looking for is a great starting point. Understanding your equipment’s temperatures, process load and flow rate allows you to bring useful information to a manufacturer so they can help you find what you need quickly.
Approaching a Chiller Project — How to Know What Size You Need
Selecting the right size chiller for a project is essential. A properly-sized chiller reliably cools equipment, stabilizes process water temperature and ensures the chiller operates at the most efficient level.
Since various industries use chillers for different applications, they come in several styles and sizes. Chiller manufacturers can help you choose the right size chiller, but understanding how to provide the right project specifications and having a general idea of what size chiller you need is significantly beneficial.
You might think that simply knowing how much flow you need is enough to size your chiller. However, many factors influence this calculation. If you’re selecting a process chiller, you can determine the right size chiller for your project based on the following factors:
- Application
- Fluid temperatures (To & From process)
- Temperature difference (Sometimes referred to as “delta T”)
- Flow rate (Typically in gallons per minute)
How to Calculate Chiller Capacity
Calculating chiller capacity is a matter of familiarizing yourself with your equipment, measuring temperatures and inputting your results into specific formulas. To calculate chiller capacity, you can follow these steps:
1. Calculate the Process Load
As an example, let’s look at a plastics application. Depending on the material you are processing, your material process temperatures will vary. Utilizing these plastics processing temperatures, along with the processing rate in pounds-per-hour of your material, you can calculate the heat load.
The sensible temperature change that occurs during material processing refers to the material’s temperature difference between when it enters and leaves the process. The result of this calculation reveals how much heat your equipment adds to the water. In this plastics process example, you also need to remove latent heat as the process transforms the plastic from a liquid state to a solid state.
To calculate sensible temperature change or delta T (ΔT), subtract your material’s temperature when it enters processing from its temperature when it exits processing. Latent heat or delta H (ΔH) serves as a safety factor in your calculations.
Since a material’s temperature remains the same as it transforms from a liquid to a solid state, there is no calculation for ΔH, but you must know the temperature so you can remove the heat from the material as it processes through this phase.
2. Calculate Chiller Size in Tons
To calculate the right size chiller you need in tons, you must first calculate the British thermal units (BTUs) per hour. Multiplying the pounds of material you process per hour by the specific heat and by the ΔT equals the BTUs per hour. (If you don’t know your material’s specific heat, don’t worry. Do a quick Google search for “thermal properties of [insert plastic name here]”). Next, you can convert the BTUs to tons by dividing the BTUs per hour by 12,000. Add a safety factor by multiplying the tons per hour by 10% or 20%.
3. Measure the Flow Rate
The easiest way to measure the flow rate is to attach a flow meter to your cooling output line. If you don’t have a meter, you can also measure the flow rate manually. Fill a five-gallon bucket with the cooling outlet, and measure how long it takes for the outlet to fill the bucket. (Note: Larger systems may require a 55 gallon can for measurement). This time measurement in GPM is your equipment’s flow rate.
4. Calculate the Actual Load
To calculate the actual load, measure your process coolant’s flow rate in gallons per minute (GPM) and determine the process coolant’s ΔT. The coolant’s ΔT is the difference between the leaving water temperature (LWT) and the entering water temperature (EWT), so you must subtract the LWT from the EWT to determine the ΔT. You can then apply your results to the formula, Q= M x C x ΔT, which consists of the following components:
- Q: In the formula, Q is the heat load measured in BTU per hour (BTUH).
- M: M equals the flow rate in GPM.
- C: C equals the fluid’s specific heat.
- ΔT: ΔT is the temperature difference represented in degrees Fahrenheit.
It’s important to remember units when calculating this formula. If your temperature is in degrees Fahrenheit, the flow should be in GPM and the specific heat should be BTU/lb(degrees)F.
5. Calculate Chiller Capacity in Tons
One ton of cooling capacity has 12,000 BTUs. The chiller tonnage calculation is Q/12,000, which converts the heat load from BTUH and reveals the correct size chiller you need in Tons of cooling. However, it’s still important to consult with a professional who can ensure you purchase the best chiller for your specific equipment and application needs.
Since your equipment may produce varying heat loads, it’s always best to size a chiller for the lowest potential temperature and the highest potential heat load a piece of equipment may produce.
Chiller Maintenance and Operating Costs
While purchasing the right chiller ensures it cools your equipment efficiently, proper maintenance is also important. Quarterly inspections help new chillers operate at their best, and monthly inspections can help chillers last longer as they age. Preventative maintenance inspections evaluate chiller performance and help to maintain the following components:
- Condenser coil and fins
- Condenser fans
- Control cabinet electrical components
- Pressure transducers
- Temperature transmitters/thermocouples
- Compressors
- Slipper seal (on some compressor types)
- Condenser
- Evaporator
Regular inspections also ensure components are free of leaks and oil seepage and operating at peak performance. While maintenance is one of the main operating costs for chillers, you also need to consider the electricity your chiller will consume.
Annual chiller operational costs typically vary between $15,828 and $38,014. Choosing an energy-efficient chiller model can help your company significantly reduce operating costs throughout the year.
Find the Right Chiller From Smart Family of Cooling Products
Understanding Chiller sizing allows you to familiarize yourself with your company’s equipment and choose the right size chiller for your applications. Smart Family of Cooling Products offers efficient industrial cooling products to help engineers cool equipment effectively while saving energy.
Our focus on industrial cooling products allows us to deliver reliable solutions, and our high-quality chillers provide cooling for demanding applications. We provide custom solutions to deliver the best cooling system based on your calculations, and our experienced team can help you choose the best option for your company’s needs. Contact Smart Family of Cooling Products to learn more and find the ideal chiller for your equipment.
