REVISTA ROMÂNĂ DE AUTOMATICĂ - IPA SA

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2.2.1. Systems with direct evaporation
For small cooling capacity (for a surface of
25÷120m 2 ), the system which imposed itself
is the one with direct evaporation, with one or
more inner units. Studies and experimental
researches regarding the performance of the
systems with direct evaporation (Table 4)
show their electric energy consumptions (Pc),
in various working conditions: ambient air
REVISTA ROMÂNĂ DE AUTOMATICĂ
temperatures, evaporation temperatures (t 0 )
and condensation temperatures (t C ), of the
common refrigerating agents used in
installations (R134a, R404A, R410A).
Romania, as a country in progress, has
benefited up until this year of facilities
regarding the Montreal Protocol exigency,
and so, in the present study the only
refrigerant taken into account is R134a, as it
is the most often used at this moment.
Table 1: COP for air conditioning systems with direct evaporation
t amb., t int t 0 , t C ,
R 134a R404A R410A
Q & ,
[°C] [°C] [°C] [°C] Pc, COP, Pc, COP, Pc, COP,
[kW]
[kW] [-] [kW] [-] [kW] [-]
30.00 20.00 8.00 45.00 9.60 2.24 4.29 2.52 3.81 2.43 3.95
32.50 20.00 8.10 47.50 9.60 2.42 3.96 2.76 3.47 2.65 3.61
32,50 20.00 8.30 50.00 9.60 2.61 3.68 3.02 3.17 2.89 3.32
37.50 20.00 8.40 52.50 9.60 2.81 3.42 3.31 2.90 3.15 3.04
40.00 20.00 8.60 55.00 9.60 3.01 3.19 3.62 2.65 3.43 2.80
The average electric consumption for homes’
air conditioning was calculated for a
functioning period of 10 hours a day, having
as a result the data in table 2.
Table 2: The performance of air-conditioning systems with direct evaporation
Living space Living Technical features of cooling plants
surface
[m 2 ] Cooling capacity, [kW] COP,
[- ]
Average consumption of
electrical power
[kWh/24h]
Studio flat 25 1.5 4,61 3,25
Ap. 2 rooms 40 2.4 4,61 5,2
Ap. 3 rooms 60 3.6 4,61 7,81
Ap. 4 -5rooms 80-120 4.8 – 7.2 4,61 10,4…15,61
2.2.2. Indirect cooling systems (with
secondary refrigerant)
In conditions identical to the ones of the
direct cooling (the same spaces, the same
inner and outer temperatures and the same
functioning period), the cooling capacity and
the driving electrical power are presented in
table 3.
Table 3. The performances of air conditioning systems with secondary refrigerant
No. Living space Living
surface
Technical features of cooling
plants
Average consumption
of electrical power
[m 2 ] Cooling capacity, COP,
[kWh/24h]
[kW]
[- ]
1. Studio flat 25 1.5 3,77 3,98
2. Ap. 2 rooms 40 2.4 3,77 6,37
3. Ap. 3 rooms 60 3.6 3,77 9,55
4. Ap. 4 -5 rooms 80-120 4.8 – 7.2 3,77 12,73…19,1
It is clearly seen that the systems with a direct 3. SPECIFIC INDICATORS