Ferroli TOP FAN Technical Bulletin - page 13
13
GENERAL SPECIFICATIONS
- Option A (unit for system with two pipes)
The technical data concerning efficiency in both the heating and cooling modes are given considering that the unit
is operated at maximum fan speed. Adequate corrective coefficients can be used to determine the efficiency ratings
at the medium and minimum speeds. In order to use Graphs 1 and 2, calculate the parameters of the requested
values considering top speed operation.
Use Tab.4
Total refrigerating capacity required at top speed Pft max = 2700/0.88 = 3070 [Watt]
Sensible refrigerating capacity required at top speed Pft max = 2100/0.84 = 2500 [Watt]
Graph 1 gives the model most able to obtain these efficiency ratings, i.e. model 40, which obtains these efficiency
ratings with a 6[°C] inlet water temperature and a
DDt of 5[°C] or 7[°C] and a DDt of 4[°C], or with an 8[°C] water inlet
temperature and a
DDt of 3[°C].
Supposing that water enters the convector fan at 7[°C] and the
DDt is 4[°C]: the water flow rate must be:
where:
Qw= Water flow rate [l/h]
DDw1= Density of the water at 10 °C [Kg/dm³]
Cpw1= Specific heat of the water at 10°C [J/kg·K]
This water flow rate obtains the expected efficiency ratings at medium speed while in this case, the effective
DDt will
be:
Graph 4 allows the relative load losses to be calculated. In this specific case, these are 35[KPa].
If the load losses were incompatible with the pump characteristics, the version with a 6 °C water inlet temperature
and
DDt of 5°C could be used. This would obtain a water flow rate of 527[l/h] instead of 659 [l/h] and a 4.4 [°C] effec-
tive
DDt at an average speed of 4.4 [°C]. In this case, Graph 4 gives a load loss of 25 [KPa].
If valve kit VB3-F is used, the additional load losses with the unit powered shown in Graph 14 are 6 [KPa] in the
first condition and 4 [KPa] in the second condition.
The optimum temperature at which the convector fan must be fed must now be found in order to obtain the requi-
red thermal power. It is reasonable to suppose that a system with two tubes operates with the same flow rate as
calculated for cold mode operation. Here again, the parameters of the required power must be re-calculated consi-
dering that the fan operates at top speed. Use Tab.5.
Thermal power required at top speed Pt max = 4000/0.85 = 4700 [Watt]
In this case, the required
DDt can be easily calculated since both the flow rate and efficiency values have already
been established. Supposing that the flow rate is 527 [l/h], one obtains:
where:
Qw= Water flow rate [l/h]
DDw2= Water density at 60 °C [Kg/dm³]
Cpw2= Specific heat of the water at 60°C [J/kg·K]
In this case, Graph 2 shows that to obtain the power required with the selected model 40, the convector fan must
be supplied with water at a temperature of about 58 [°C]. As shown in Tab.4 attached to Graph 4, note that the load
losses are less than those obtained in cold mode by a factor of about 0.77. It is therefore logical to expect a higher
water flow rate than the one estimated if the circuit pump characteristics are to remain the same. In this case, the
water flow for which the load losses are 25 [KPa] is about 650 [l/h], as can be seen from the same graph.
Tab.9 can thus be used to calculate the value of the noise generated by the selected unit which, as mentioned pre-
viously, is model 40 operating at medium speed, thus an acoustic power of 47 dB[A] and a corresponding sound
pressure of 38 dB[A], measured according to the indicated conditions.
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/
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4192
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3600
3070
cp
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2700
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