Exercise : Selecting an electronic expansion valve
Select an electronic expansion valve for a chiller, from the product family ‘ETS Colibri®’, with the following operating conditions:
- Refrigerant: R513A
- Cooling capacity: 90 kW
- Evaporator temperature: 3 °C
- Useful superheat: 8 K (Default)
- Condenser temperature: +40 °C
- Subcooling: 3 K
a). Which target load should be put in the selection criteria and why?
b). Which valve size will be recommended for that target load (if you have chosen a range for the load, use the upper limit of the range for this input)?
c). What is the velocity at the valve inlet for the suggested valve?
d). Is there an alternative to the valve suggested by Coolselector®2 in the selection list with the same load at nominal conditions? What is the difference between the two valves and why is there a difference? Please explain.
e). Please explain, what is the minimum possible capacity and opening degree for the valve suggested by Coolselector®2 in b)?
f). Would there be a risk if you select ETS Colibri 100C electronic expansion valve? Please explain using a chiller application as an example.
g). What would be the suggested valve if we want to replace the valve with one from the AKV family?
1. What is the difference between the two families, ETS and AKV?
2. What would be the actual speed at the inlet of the suggested expansion valve?
Solution : Selecting an electronic expansion valve
Similar to the previous exercise, set the system to ‘Dry’ and then select the liquid line. Next, please select the refrigerant (R513A) and the Product Family (ETS Colibri):
a). For both air condition and refrigeration systems, the recommended selection criteria for ‘load’ is about 70% to 80%. By setting the load like this, there is 20% to 30% capacity left, for example for pull-down.
As is evident, the more over-capacity the system requires, the lower the load should be set in the selection criteria.
For low temperature applications it is recommended to size the electronic expansion valve at 50-60%. Otherwise, the pull-down capacity might be insufficient.
b). Based on the selection criteria and a load set to 80%, Coolselector®2 suggest the ETS Colibri 24C-22 as the best match:
C). The liquid velocity at the inlet connector is about 1.80 m/s. You can find the liquid velocity in the selection table:
d). An alternative would be the ETS Colibri 25C, since this has the same load percentage (78%) as the ETS Colibri 24C-22:
The ETS Colibri 24c-22 and the ETS Colibri 25C valves are exactly the same in performance, which you can see in the calculation results. The only difference is that ETS Colibri 25C is equipped with a side glass, while ETS Colibri 24C-22 does not have the side glass.
You can contact Danfoss or your supplier for more information or if you have any questions regarding the products and you require assistance with your selection.
e). The minimum capacity for the ETS Colibri 24C-22 at the given operating conditions is 15.66 kW at around 10% opening of the valve. You can find the minimum capacity in the selection table.
Furthermore, you can see this in Coolselector®2 if you use the performance curve shown underneath the selection table. Move your mouse to the desired cooling capacity [kW] on the x-axis to see the corresponding opening degree [%] on the y-axis:
f). ETS Colibri 100C has a higher max capacity of about 428.5 kW, as is evident from the selection table in Coolselector®2:
This would be more than enough capacity for running the system under full load conditions as well as pull-down. However, in the event that the chiller runs into part load, the size of the ETS Colibri 100C might become an issue since its minimum possible capacity is 39.01 kW. Thus, the ETS Colibri 100C may be too large for this system.
As is evident from the example above, it is always recommended to verify if the valve is suitable for the whole envelope of the system, considering both loads and extreme conditions.
g). To replace the valve with one from the AKV family, we need to click on the AKV in the “Product families” list:
- AKV is a family of pulse width modulated expansion valves. This means the valve is either fully open or fully closed. As a result, while the valve is open, the capacity is the maximum capacity.
- To calculate the actual velocity for AKV or any of the pulse width modulated expansion valves, you should replace the capacity to the maximum capacity of the valve. You will see that for AKV 20-2 the velocity at the inlet would be 0.73 m/s:
|Type||Name||Language||Valid for||Updated||Download||File type|
|Promotion material||Coolselector®2 Exercises||English||Multiple||04 Jun, 2019||13.5 MB|
|Installation guide||Coolselector®2 Server Installation Guide||English||Multiple||18 Nov, 2020||1.2 MB|
|User guide||Coolselector®2 User Guide||English||Multiple||04 Jun, 2019||4.4 MB|
|User guide||Coolselector®2 User Guide||Spanish, Castilian||Spain||25 Feb, 2020||5.8 MB|
|User guide||Coolselector®2 User Guide||French||France||05 Mar, 2020||5.5 MB|
|User guide||Coolselector®2 User Guide||Portuguese||Multiple||03 Jan, 2020||5.3 MB|
|User guide||Coolselector®2 User Guide||Russian||Russia||25 Feb, 2020||4.4 MB|
|User guide||Coolselector®2 User Guide||Chinese (CN)||Switzerland||04 May, 2020||25.2 MB|
Our training videos are constructed to give you an introduction to each of the main areas of Coolselector®2. The videos show examples of use cases as well as useful tips and tricks for every day use.