HeatRecoveryUnit¶
Balanced ventilation with a constant-effectiveness heat recovery and constant-pressure fans (trano's system D); the reference of its air loop
FastSmoothBuildings.Ventilation.HeatRecoveryUnit, model (source)
Purpose
Air handling unit of a balanced ventilation (trano's system D): outdoor air through a heat recovery of constant
effectiveness, warmed by constant-pressure fans, and the electricity of the fans metered. The unit is the reference
of its air loop: it sets the speed y that the ducts downstream turn into their flows, and the supply
air temperature.
Equations
Mixed extract air temperature, regularised by m_flow_small so that it is defined at zero flow (the
mean of the port temperatures):
TExt = (∑ ṁi Ti + ṁsmall ∑ Ti/n) / (∑ ṁi + ṁsmall).
Supply air and fans:
TSup = TDryBul + ε (TExt − TDryBul) + ΔTFan, PFan = y (PSup + PRet), dEFan/dt = PFan/3.6·106 (kWh),
with the fan powers at nominal flow PSup = ΔpSup ṁnominal/(ρAir ηFan), likewise PRet, and the heating of the supply air by the fans (supply fan after the exchanger, return fan before it) ΔTFan = (PSup + ε PRet) / (ṁnominal cp). The power of constant-pressure fans and the flow are both proportional to y, so ΔTFan is the same at every speed.
Parameters
| Name | Default | Meaning |
|---|---|---|
m_flow_nominal | nominal supply flow | |
eps | 0.8 | heat recovery effectiveness |
dpSup_nominal, dpRet_nominal | 200 Pa | pressure rises of the supply and return fans |
etaFan | 0.5 | overall efficiency of the fans |
m_flow_small | 10−6 kg/s | regularisation of the mixed extract temperature |
nPorts_a, nPorts_b | 1 | numbers of extract and supply connections |
Use
Connect the weather to weaBus, the supply port_b through a
Duct to a
Zones.VentilatedZone and its extract back through
another duct to port_a, as in
Examples.VentilatedRoom.
Parameters¶
| Parameter | Type | Unit | Default | Description |
|---|---|---|---|---|
| nPorts_a | Integer | 1 | Number of extract connections | |
| nPorts_b | Integer | 1 | Number of supply connections | |
| m_flow_nominal | Real | kg/s | Nominal supply flow | |
| eps | Real | 0.8 | Heat recovery effectiveness | |
| dpSup_nominal | Real | Pa | 200 | Pressure rise of the supply fan |
| dpRet_nominal | Real | Pa | 200 | Pressure rise of the return fan |
| etaFan | Real | 0.5 | Overall efficiency of the fans | |
| m_flow_small | Real | kg/s | 1e-6 | |
| PSup | Real | W | dpSup_nominal*m_flow_nominal/rhoAir/etaFan | Supply fan power at nominal flow |
| PRet | Real | W | dpRet_nominal*m_flow_nominal/rhoAir/etaFan | Return fan power at nominal flow |
| dTFan | Real | K | (PSup + epsPRet)/(m_flow_nominalcpAir) | Heating of the supply air by the fans (supply after the exchanger, return before it) |
Revisions¶
- October 2026: moved from trano's
FastModel.Ventilation.