Equithermal Curve (v1.0)
Full Name
Lib.Mervis.v1_0.EquithermalCurve
Required Project References
- Lib.Mervis
Description
Block for calculating the heating medium temperature according to the equithermal curve.
Usage in ST
program test
var
eq: lib.mervis.v1_0.EquithermalCurve;
end_var
eq();
end_program
Inputs
| Inputs | Name | Data Type | Retain | Mandatory Connection | Meaning |
| In | real | No | Yes | Outdoor temperature | |
| t_i | real | Yes | No | Calculated indoor temperature | |
| t_emin | real | Yes | No | Minimum outdoor temperature | |
| t_w1max | real | Yes | No | Maximum heating medium temperature | |
| t_w2max | real | Yes | No | Minimum heating medium temperature | |
| n | real | Yes | No | Temperature exponent |
Outputs
| Outputs | Name | Data Type | Meaning |
| t_flow | real | Calculated heating medium temperature | |
| t_return | real | Calculated return heating medium temperature |
Detailed Function Description
The block calculates the required heating medium temperature inversely to the outdoor air temperature to maintain balance between heat input and building heat losses.
The calculation relies on the following mathematical formulas:
Medium Cooling ($\Delta t$): $$ \Delta t = (t_{w1,max} - t_{w2,max}) \cdot \frac{t_e - t_i}{t_{e,min} - t_i} \quad [K] $$
Mean Medium Temperature ($t_m$): $$ t_m = t_i + \left(\frac{t_{w1,max} + t_{w2,max}}{2} - t_i\right) \cdot \left(\frac{t_e - t_i}{t_{e,min} - t_i}\right)^{\frac{1}{n}} \quad [^\circ C] $$
Recommended values for the parameter n:
| Heating Type | Parameter n Value |
|---|---|
| Underfloor heating | 1.10 |
| Panel radiators | 1.26 to 1.33 |
| Tubular bathroom radiators | 1.20 to 1.30 |
| Radiators according to DIN 4703 | 1.30 |
| Convectors | 1.30 to 1.50 |