Development of multi-function CO2 Heat Pump Water Heater

Development of multi-function CO2 Heat Pump Water Heater

Background of multi-function water heater Market trend of gas combustion multi-function water heater X1000 400 200 1996 1997 1998 1999 2000 2001 2002 2003 Market of multi-function hot water heater is is glowing Energy consumption at residence Annual report of residential energy statistics (1999) Proceed energy saving based on Top Runner Approach standards of energy efficiency Lighting, electric appliances e.t.c. Cooling 2.4% 36.3% Hot water feed 33.8 Space heating 27.5% year Need to develop high efficiency system

Main task of multi-function heat pump water heater Characteristics of multi-function system Use hot water in the storage tank directly for hot tap water Use hot water in the storage tank indirectly for heat source of space heating Heat pump unit Water-Ref. HE. Ejector Evap. Compressor Higher temp. water than feed water Tank unit 90 90 Tap water 90 70 Tank 90 70 High temp. 55 Feed-water Primar y heating circuit 45 Secondary heating circuit Water - Brine HE 40 Bath Shower Space heating Main problem Return water from primary heating circuit is mixed into cold feedwater Heat pump COP becomes down with higher inlet water temp.

Countermeasures of task pressure Characteristics of CO2 heat pump Decline of heating capacity and cop under high inlet water temp. cond. Isotherm. high Heating capacity Heating capacity Higher inlet water temp. 9 40 60 Electric power Countermeasures for decline of COP To use return water for tap water ( medium temp. water) Development of Cascade heat process system To improve heat pump cop at higher inlet water temp. condition Development of ejector cycle for heat pump water heater enthalpy

Outline of cascade heat process system H/P Conventional storage tank Medium temp.water can not use Heat pump COP becomes down Space heater H.EX Primary heating circuit 45 Medium temp. water 9070 470 0 35 mix valve Feed-water 9 Hot tap water higher temp. water interrupt Medium temp. water Medium temp. water and cold feed-water flow into tank by turns. Too low temp. for hot tap water Cause inlet water temp.. for heat pump rising and COP becomes down 2 additional water return ports for primary heating circuit to prevent to mix water 2 additional outlet ports to use medium temp.water for hot tap water Space heater Switching valve H/P Cascade heat process system Characteristics HEX 9070 45 470 7035 9 Change return port to keep temperature layer Hot tap water Switching valve Change outlet port to take medium temp. water out 3 different temp. water in the 3 portions of the storage tank

Optimization of port position for cascadeheat process system Basic idea: Fit for general working pattern 55 70 Space heater 45 Return port H/P 90 70 90 470 70 45 320L 70 45 35 9 Feed-water Tank volume 460L hot tap water Outlet port <Optimization of upper additional outlet port> Potential amount of hot tap water (43) amount of boundary layer (L) 300L 250L 200L 150L 60 45 30 15 280 300 320 340 360 outlet port position amount of hot tap water :IBEC L mode, floor heating aria 13.2m2 operation time 8hr, ambient temp. 7, feed-water temp.9 Characteristic of boundary layer < between hot and cold water > Simulation analysis Test result 5 15 45 85 deference of temp. t=t T2 above 15, boundary layer can form

Evaluation result of cascade heat process system Amount of water 85 operation pattern of tap water, floor heating, bathroom heating 400 300 200 100 :hot tap water floor heating floor heating 4h water feed for bath tab bathroom heating shower simulation analysis- heating water operation by heat pump 6 00 8 00 10 00 12 00 14 00 16 00 18 00 20 00 22 00 0 00 2 00 4 00 6 00 tap water: IBEC L mode floor heating: aria 13.2m2, 8hr bathroom heating: heating capacity 2kW 20min ambient temp. :7 feed-water temp. : 9 position of storage tank 500 450 400 350 300 250 200 150 100 50 0 6:00 7:00 Conventional tank system 8:00 9:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00 20:00 21:00 22:00 23:00 0:00 1:00 2:00 3:00 4:00 5:00 6:00 above 70 70 35 35 20 20 position of storage tank 500 450 400 350 300 250 200 150 100 50 0 6:00 7:00 Cascade heat process system 8:00 9:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00 20:00 21:00 22:00 23:00 0:00 1:00 2:00 3:00 4:00 5:00 6:00 above 70 70 35 35 20 20

Outline of ejector cycle pressure Ejector cycle for CO2 heat pump Kinetic energy loss of CO2 is 3 times higher than HFCs CO 2 kinetic energy loss HFCs enthalpy Ejector cycle Higher inlet water temp. Benefit of ejector cycle Condition Ambient temp.() feed-water temp.( Winter 7 9 Intermediate 16 17 Summer 25 24 JRA4050 standard 5.0 4.5 10UP Driving flow Ejector evaporator mixture section Pressure rise COP 4.0 3.5 3.0 6.0W conventional 6.0W ejector P H P S P D needle P L Suction flow nozzle diffuser Ejector with variable nozzle 2.5 Winter Intermediate Summer

Summary 1. We have developed cascade heat process system, and have evaluated this performance at field test. 2. We have started to product multi-function CO2 heat pump water heater using variable nozzle ejector cycle at July 2003.