Figure 1.
HRU-WALL-100-25 compact recuperator and its dimensions in millimeters [11]
Figure 2.
Air temperature test stand
Figure 3.
Location of the thermocouples; 1) in the air intake, 2) in the outdoor environment, 3) between the heat exchanger and the fan, 4) behind the fan (air inlet to the room), 5) in the room
Figure 4.
Scheme of air velocity distribution test stand
Figure 5.
Tube halves printed in a 3D printer
Figure 6.
Sample graph of air temperatures for the second fan speed at balanced pressures in the room and outside
Table 1.
Calculated supply efficiency for the tested working conditions
| Working conditions | Supply efficiency |
|---|---|
| third fan speed at balanced pressures | 64% |
| second fan speed at balanced pressures | 68% |
| first fan speed at balanced pressures | 79% |
| third fan speed at a natural pressure difference | 56% |
| second fan speed at a natural pressure difference | 47% |
Table 2.
Calculated exhaust efficiency for the tested working conditions
| Working conditions | Exhaust efficiency |
|---|---|
| third fan speed at balanced pressures | 73% |
| second fan speed at balanced pressures | 83% |
| first fan speed at balanced pressures | 85% |
| third fan speed at a natural pressure difference | 79% |
| second fan speed at a natural pressure difference | 93% |
Table 3.
Calculated averaged air flow volume rate for all fan speeds based on measurements for 0 Pa
| Air supply | 0 Pa |
|---|---|
| first fan speed | 9 m3/h |
| second fan speed | 16 m3/h |
| third fan speed | 28 m3/h |
| Air exhaust | 0 Pa |
| first fan speed | 8 m3/h |
| second fan speed | 14 m3/h |
| third fan speed | 29 m3/h |
Table 4.
Calculated averaged air flow volume rate for all fan speeds based on measurements for 4 Pa
| Air supply | 4 Pa |
|---|---|
| first fan speed | 14 m3/h |
| second fan speed | 20 m3/h |
| third fan speed | 32 m3/h |
| Air exhaust | 4 Pa |
| first fan speed | 2 m3/h |
| second fan speed | 12 m3/h |
| third fan speed | 27 m3/h |
Table 5.
Calculated averaged air flow volume rate for all fan speeds based on measurements for 7 Pa
| Air supply | 7 Pa |
|---|---|
| first fan speed | 19 m3/h |
| second fan speed | 22 m3/h |
| third fan speed | 36 m3/h |
| Air exhaust | 7 Pa |
| first fan speed | -8 m3/h |
| second fan speed | 6 m3/h |
| third fan speed | 25 m3/h |
Figure 7.
Air velocity profile for supply mode (left) and exhaust mode (right) for third fan speed and 0 Pa of pressure difference