General¶
Below are instructions on how to set operating conditions, add heat pumps, and how to use different functions to set up your heat pumps system for calculation.
Setting operating conditions¶
Changing refrigerants¶
Setting compressors to part load¶
Connecting heat pumps in series¶
Checking if the installation space has a sufficient volume¶
When using flammable refrigerants (such as R1234ze), the installation site must have a sufficient volume. In cramped spaces, a ventilated enclosure is required.
To check if the volume of the installation space is sufficient:¶
Select the heat pump model.
To select the refrigerant, right click on the heat pump image. Select Refrigerant and select the refrigerant from the list.
Click the Placement button.
Select the applicable options and enter the area and average height of the space, or enter the volume of the space directly.
Open the second tab (P150 in the image). Compare the refrigerant charge with the maximum allowed charge.
If the refrigerant charge is greater than the maximum allowed charge, a ventilated enclosure is required. See add a ventilated enclosure for a heat pump.
Reference standards¶
- Refrigerant charge limits and formulas
EN378-1 Annex C
Adding a ventilated enclosure for a heat pump¶
Sound levels¶
Sound levels at specific operating points¶
Unfortunately, it is currently not possible to estimate sound levels at specific operating points. The best available information is provided by the Oilon Selection Tool. The estimated sound levels vary by 3 dB(A) depending on the operating conditions.
Minimum allowed flow through the heat exchangers¶
For ChillHeat heat pumps that use plate heat exchangers (P30 - P450, RE210 - RE420, S180 - S580), there is no minimum required water/brine flow. If the flow is small enough to cause issues with heat transfer, the effect is taken into account in the heat exchanger simulation (the performance of the heat pump will degrade).
Contact Oilon HQ to check the minimum allowed water/brine flow of ChillHeat heat pumps that use shell and tube heat exchangers.
Maximum allowed flow through the heat exchangers¶
By default, the maximum allowed flow through the heat exchangers is defined so that the flow velocity is < 5.5 m/s in the heat exchanger connections. The purpose of the limit is to prevent the possibility of erosion in the heat exchanger connections. You will receive a warning if the flow velocity exceeds this limit. However, the limit is not absolute and exceptions can be made. A greater flow can be allowed if the water can be determined to be free of solid particles, such as sand or metal particles. If, for example, a water analysis has been conducted and the water is determined to be free of solid particles, the maximum allowed flow can be increased.
Operation limits chart¶
The operation limits chart demonstrates the allowed operational limits for the heat pump. The chart is similar to the operation envelope that compressor manufacturers provide for their compressors. The differenc is that the operation limits chart takes several other components of the heat pump into account, not only the compressor. There are three distinct areas in the operation limits chart.
Restricted minimum capacity area. The minimum allowed part load in this area is higher than the absolute minimum possible part load of the compressors. For example, if the compressors would allow a part load of 25% for the heat pump but the operating point is in this area, the minimum allowed part load may increase from 25% to 35%. The minimum part load is limited by the super heat control and expansion valve; a stable superheat must be ensured to ensure a long lifetime for the heat pump.
Full capacity operational area. The heat pump can be operated at full (100%) capacity in this area.
Reduced capacity area. The heat pump can operate in this area. However, you will not achieve the full power output as predicted by OST. In this area, the selected expansion valve is too small, leading to a restricted flow of refrigerant and to a power output reduction.
Connection modules¶
Connection modules allow you to make creative connections in the evaporator water circuit.
Individual temperatures¶
Connection modules can have individual inlet and outlet temperatures. In order to use the functionality, follow the steps below.
Insert your condenser temperatures and evaporator temperatures in the main evaporator circuit.
Select PARALLEL as the evaporator connection type.
Select your heat pumps. Your selection should now look as shown below.
Click on the cog wheel on the evaporator connection type and set the amount of connection modules.
Click on the cog wheel on the evaporator inlet temperature.
Enable individual temperature of the connection module 1
Set the inlet and outlet temperature for this circuit.
Click on the Details button on the tool bar.
Set the first heat pump to the first connection module and the second heat pump to the second connection module.
Go back to the wireframe and calculate. Your selection should now look as shown below.
Subcooler with separate inlet temperature¶
The Subcooler with separate inlet temperature selection can be used if the subcooler of the heat pump is connected to a separate flow which will be merged with the condenser flow before entering the condenser. The connection is demonstrated in the image below. The inlet temperature to the heat pump is 40 °C, but there is a separate flow of 20 °C that is fed into the subcooler. Before the flow enters the condenser, the subcooler flow is merged to the condenser.
