p3: heat pump systems with co2 as working fluid
TRANSCRIPT
Presentationsmaterial EFFSYS 2 dagen 2008-11-11
P3: Heat pump systems with CO2
as working fluid Experimental Investigation of the Performance of a
Carbon Dioxide Heat Pump
Yang Chen & Per Lundqvist
Div. of Applied Thermodynamics and RefrigerationDept. of Energy Technology
Royal Institute of TechnologySweden
Presentationsmaterial EFFSYS 2 dagen 2008-11-11
Contents• General info. about Sanyo Eco-cute
• Tests and results– Heat pump performance – System performance– Defrosting – Tank performance
• Comments
• References
Presentationsmaterial EFFSYS 2 dagen 2008-11-11
General info. about Sanyo Eco-cute•The first CO2 heat pump for the Swedish market ,which was released by Ahlsell on July 10th, 2005
•Capacity-controlled by a variable-speed control (inverter).
•An air source heat pump provides both space heating and domestic hot water (DHW) heating.
•It is claimed to deliver 4.5 kW heat power down to an outdoor air temperature of -15 °C and to be able to heat the water up to +70 °C.
Presentationsmaterial EFFSYS 2 dagen 2008-11-11
Transcritical cycle
-1.75 -1.50 -1.25 -1.00 -0.75 -0.50-25
0
25
50
75
100
s [kJ/kg-K]
T [°
C]
135 bar
90 bar
55 bar
35 bar
0,2 0,4 0,6 0,8
0,0
017
0,0
057
0,0
1
0,0
63 m
3/kg
a40 Bar
b
c
d
e
f
Carbon DioxideTranscritical Cycle
Presentationsmaterial EFFSYS 2 dagen 2008-11-11
Performance Testing (COP)COP vs. Water inlet temp. to GC
1
1.5
2
2.5
3
3.5
10 15 20 25 30 35 40 45
Water inlet temperature to the gas cooler
CO
P
0 °C 7 °C -5 °C -10 °C
Presentationsmaterial EFFSYS 2 dagen 2008-11-11
COP comparison with manualManual: 30/50 °C water inlet and outlet gas cooler
7 °C outdoor temperature: 30.1 / 59.2 °C COP 2.91 3.1
20 °C outdoor temperature:30.4 / 51.6 °C COP 4.2 3.75
Presentationsmaterial EFFSYS 2 dagen 2008-11-11
System testing condition
• Including the tank and radiator system in analysis
• Defined load cases at different Tamb:
– 4,7 kW – 8K deltaT; 0,50m3/h– 3,0 kW – 8K deltaT; 0,33m3/h– 2,9 kW – 5K deltaT; 0,50m3/h– 1,9 kW – 5K deltaT; 0,33m3/h
• Stable condition is maintained for ca. 30 mins. before the averaged values are taken
heating load as funcion of deltaT for different mass flow rates[m3/h]
0
1
2
3
4
5
6
7
0 1 2 3 4 5 6 7 8 9 10 11 12deltaT [degreeC]
pow
er o
utpu
t [kW
]
0,2 0,25 0,3 0,35
0,4 0,45 0,5
mass flow rates [m3/h]
Presentationsmaterial EFFSYS 2 dagen 2008-11-11
Frosting/defrosting tests - layout
• Pos. 1/2 represent theboiler position
• Position 1: strong moisture condition
• Position 2: normal condition
Presentationsmaterial EFFSYS 2 dagen 2008-11-11
Test restult at pos.1 at -2°CFrosting-defrosting periods at -2 degreeC Tamb and 3,4kW heating load
2008-04-14
-20
-10
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
0 1800 3600 5400 7200 9000 10800 12600 14400 16200 18000 19800 21600 23400
time[s]
tem
pera
ture
[C]
-12
-11
-10
-9
-8
-7
-6
-5
-4
-3
-2
-1
0
1
2
3
4
5
6
heat
ing
capa
city
[kW
]; flo
w [-
]; CO
P [-]
; pow
er [k
W]
evap. air in
evap. air out
CO2 compr. In
water gas cooler in
water gas cooler out
CO2 Exp.-valve in
CO2 compr. Out
Comp
normalized flow[x/0,239]heating capacity
COP
problem in data logging
defrosting periods
temperature approach before defrosting
1st 2nd
Presentationsmaterial EFFSYS 2 dagen 2008-11-11
Frosting-defrosting periods at -2 degreeC Tamb and 3,4 kW heating load 2008-04-14 - detail of first two cycles
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
105
1800 3600 5400 7200 9000
time[s]
CO
2 co
mpr
. out
, CO
2 Ex
p.-v
alve
in,
wat
er g
as c
oole
r in[
°C]
-20
-17,5
-15
-12,5
-10
-7,5
-5
-2,5
0
2,5
5
7,5
10
12,5
15
17,5
20
Teva
p bo
ttom
/mid
, CO
2 co
mpr
. in,
eva
p. a
ir in
/out
[°C
];
CO
P[-]
; flo
w[-
];
water gascooler in
CO2 Exp.-valve in
CO2 compr.Out
evap. air in
evap. air out
CO2 compr.In
normalizedflow[x/0,239]COP
Tevapbottom
Tevap mid
Detail view at -2°C of frosting / defrosting
Presentationsmaterial EFFSYS 2 dagen 2008-11-11
Development of Freezing Protection•Stop the ice from building up at the bottom of the evaporator
EvaporatorPipe thickness 0.6 mm
Warm CO2Pipe thickness 0.9 mm
Freezing protection
circuit
•Warm CO2 after the gas cooler is leaded to the bottom of the evaporator
•No electrical-heater needed
Air flow
Presentationsmaterial EFFSYS 2 dagen 2008-11-11
Water tank performance
• Tank behaviour is important for the heat pump performance
• Good temperature stratification can ensure better heat pump performance
• Thermocouple position in figure
T1
T2
T3
T4
T5
T6
Presentationsmaterial EFFSYS 2 dagen 2008-11-11
Charging freshly filled tanktank charging with electric heater at -2°C Tamb - 2008-04-29
0
5
10
15
20
25
30
35
40
45
50
55
60
65
70
0 900 1800 2700 3600 4500 5400 6300 7200 8100 9000 9900 10800 11700
time [s]
tem
pera
ture
[°C
]
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Flow
[m3/
h]; p
ower
[kW
]; C
OP
[-]
T_top
T1
T2
T3
T4
T5
T6
water gascooler outwater gascooler indeltaT_strat
compr. power
Flow scaled 10[m3/h]COP
el. heater stops
Presentationsmaterial EFFSYS 2 dagen 2008-11-11
Charging freshly filled tanktank charging with no electric heater at -2°C - 2008-05-01
0
5
10
15
20
25
30
35
40
45
50
55
60
65
70
0 900 1800 2700 3600 4500 5400 6300 7200 8100 9000 9900 10800 11700
time [s]
tem
pera
ture
[°C
]
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Flow
[m3/
h]; p
ower
[kW
]; C
OP
[-]
T_top
T1
T2
T3
T4
T5
T6
water gas coinwater gas cooutdeltaT_strat
compr. Powe
flow scaled 1[m3/h]COP
Presentationsmaterial EFFSYS 2 dagen 2008-11-11
Comments• The testing of heat pump performance shows that the
European heat pump testing standard EN14511 can not give a fair comparison between CO2 heat pump and traditional heat pump.
– a high water inlet temperature – a small temperature lift
• The heat pump COP testing shows simimlar results as the values specified in the user manual
Presentationsmaterial EFFSYS 2 dagen 2008-11-11
Comments• During the system testing, the heat pump system
achieves a lower system COP than conventional heat pumps, which is mainly due to the reason that the water tank delivers water to the CO2 heat pump at an unfavorable high temperature
• The defrosting test shows that the start point of defrosting mode is controlled by the temperature difference between the evaporator air inlet temperature and evaporator temperature, which can indicate the ice blocking up the air flow path through the fins
Presentationsmaterial EFFSYS 2 dagen 2008-11-11
Comments
• The testing results show that the tank is a critical component to improve the system performance
• Several mesurements can be done to iimprove stratification in the tank:
– Sensor position in the tank– Connecting tubes position
Presentationsmaterial EFFSYS 2 dagen 2008-11-11
Reference• Project reference:
• Poster• Conference paper
• Eco-cute testing reference• Experimental Investigation of the Performance of a
Carbon Dioxide Heat Pump-------- Leonie Brachert• Heat pump testing report ----------André Alves• Testing of a CO2 heat pump sold in Swedish market
(Sanyo-Ecocute)-------- Yang Chen