Investigations of Heat Recovery in Different Refrigeration System Solutions in Supermarkets

Transcription

1 Investigations of Heat Recovery in Different Refrigeration System Solutions in Supermarkets Samer Sawalha Department of Energy Technology Kungliga Tekniska Högskola Stockholm-Sweden 2008

2 Project background Main objectives Methods of analysis Modelling Field tests Experimental work Outline Summary of the work Ongoing and future tasks

3 Project background Research work at the Energy Technology department at KTH: CO2 in Supermarket Refrigeration Investigate whether CO2 is a good alternative solution for supermarket refrigeration (theoretically and experimentally) Compare CO2 systems to a conventional/alternative system solution The investigated CO2 systems are efficient solutions for supermarket refrigeration

4 Systems total COP 7 Centralized 6 5 R404A NH3/CO2 Cascade DX R404A float Modified Centralized 2 St. Centralized CO2 Parallel, 2-St. Low and Med COPtot [-] 4 3 R404A Indirect at Medium R404A Indirect at Med (No pump) Cascade 2 1 Evaporation temperature: Modified centralized (-30/-4 C) R404A float (-33/-8 C) R404A Indirect (-33/-16 C) Tamb [ºC]

5 Trans-critical Parallel Focus was on the cold side of the system.

6 Main objectives of current project Investigate the heat recovery performance of the new system solutions System modifications and optimizations will take into account not only the cooling efficiency but also the efficient heat recovery according to the needs in the supermarket

7 Modelling Method Create daily and seasonal profiles (capacity and needs at which temp) Different system solutions Field tests Collecting data from supermarket installations Experimental work Evaluation of key components (CO2 system)

8 Supermarket systems Modelling R404A conventional (brine at medium temperature) CO2 pump circulation CO2 trans-critical Parallel system Centralized (booster) Cascade R404A/CO2 Ammonia/CO2

9 Modelling: R404A conventional T con,b,i = 32 [C] T con,b,o = 36 [C] Q con,tot = 292,2 [kw] dt sc,m = 3 [C] T con,m,in = 58,84 dt sc,f = 3 T con,m = 39,26 [C] Q con,m = 208,6 [kw] η is,m = 0,8 T con,f = 39,26 [C] Q con,f = 83,62 [kw] T con,f,in = 70,3 [C] COP f = 1,586 COP m = 2,56 COP tot = 2,22 dt sh,m = 7 [C] T ev,m = -16 [C] dt sh,ex,m = 0 η is,f = 0,8 Heat rejection capacities Q con,tot = 292,2 [kw] dt sh,ex,f = 5 Q desup,tot = 53,33 [kw] Q condensation,tot = 229,8 [kw] Q sc,tot = 9,063 [kw] Low temperature desuperheater Q desup,f = 19,32 [kw] E m,pump = 0 Q f = 50 [kw] T ev,f = -33 [C] T con,f,in = 70,3 [C] T desup,f,b,i = 29,26 T desup,f,b,o = 60,3 Q m = 150 [kw] dt sh,f = 7 [C] Medium temperature desuperheater Q desup,m = 34,01 [kw] T con,m,in = 58,84 T desup,m,b,i = 29,26 T desup,m,b,o = 48,84

10 Modelling Perecentage of total heat rejection 100% 90% 80% % of total heat rejection 70% 60% 50% 40% 30% Q De-supuerheating total Q Sub-cooling Q Condensation total 20% 10% 0% R404A conventional R404A/CO2 indirect R404A/CO2 cascade Ammonia/CO2 cascade CO2 Trans-critical Parallel

11 90 80 Modelling De-superheating capcitites Heat Capacity (kw) Freezer Medium/High stage 38 T in =80 C T in =170 C 30 T in =70 C T in =70 C T in =58 C T in =58 C T in =74 C T in =74 C 0 R404A conventional R404A/CO2 indirect R404A/CO2 cascade Ammonia/CO2 cascade

12 Modelling Perecentage of total heat rejection 100% 90% 80% % of total heat rejection 70% 60% 50% 40% 30% Q De-supuerheating total Q Sub-cooling Q Condensation total 20% 10% 0% R404A conventional R404A/CO2 indirect R404A/CO2 cascade Ammonia/CO2 cascade CO2 Trans-critical Parallel

13 Modelling CO2 solutions has different 250 range of: heat capacities 200 Heat rejection temperatures and temperature profiles Heat Capacity (kw) CO2 trans-critical heat rejection capcitites Q Intercooler T in=110 C Q Heat rejection Fr Q Heat rejection Med T in=130 C 0 T in=100 C 9 CO2 Trans-critical Parallel

14 100 R404A Modelling 200 Ammonia T [ C] 40 T [ C] ,20 0,40 0,60 0,80 1,00 Temperature profile s on [kj/kg-k] the heat rejection side Study the performance of the CO2 heat rejection side in sub- and trans-critical operation. How can the flow of heat rejection be arranged to produce good match between the refrigerant and heat sink temperature? How can the system be controlled to produce good heat rejection performance? T [ C] 0 CarbonDioxide 120 1,0 2,0 3,0 4,0 5,0 6,0 7,0 110 s [kj/kg-k] ,75-1,50-1,25-1,00-0,75-0,50 s [kj/kg-k]

15 Heat recovery and floating condensing 2 x 10 3 R404A 2 x 10 3 Ammonia 40 C T heat;sink =30 C C P [kpa] 10 3 T heat;sink =10 C P [kpa] 2x C h [kj/kg] C CarbonDioxide h [kj/kg] C T heat;sink =30 C By modeling, and experimentally in case of CO2 system, the influence of floating condensing on heat rejection capacities will be examined. P [bar] T heat;sink =0 C -20 C x h [kj/kg]

16 Field tests The field testing work is in cooperation with IUC- SEK at Katrineholm The main objective is to invistigate the cooling performance of different refrigeration system solutions in supermarkets Measurments will be extended to include the heat recovery side in the refirgeration systems

17 Modelling: R404A conventional T con,b,i = 32 [C] T con,b,o = 36 [C] Q con,tot = 292,2 [kw] dt sc,m = 3 [C] T con,m,in = 58,84 dt sc,f = 3 T con,m = 39,26 [C] Q con,m = 208,6 [kw] η is,m = 0,8 T con,f = 39,26 [C] Q con,f = 83,62 [kw] T con,f,in = 70,3 [C] COP f = 1,586 COP m = 2,56 COP tot = 2,22 dt sh,m = 7 [C] T ev,m = -16 [C] dt sh,ex,m = 0 η is,f = 0,8 Heat rejection capacities Q con,tot = 292,2 [kw] dt sh,ex,f = 5 Q desup,tot = 53,33 [kw] Q condensation,tot = 229,8 [kw] Q sc,tot = 9,063 [kw] Low temperature desuperheater Q desup,f = 19,32 [kw] E m,pump = 0 Q f = 50 [kw] T ev,f = -33 [C] T con,f,in = 70,3 [C] T desup,f,b,i = 29,26 T desup,f,b,o = 60,3 Q m = 150 [kw] dt sh,f = 7 [C] Medium temperature desuperheater Q desup,m = 34,01 [kw] T con,m,in = 58,84 T desup,m,b,i = 29,26 T desup,m,b,o = 48,84

18 Supermarket systems Field tests R404A conventional (brine at medium temperature) CO2 pump circulation CO2 trans-critical Parallel system Centralized (booster) Cascade R404A/CO2 Ammonia/CO2

19 Experimental work-co2 system Building a test rig which runs as a heat pump Ready to be installed in the lab Evaluation of Key components Heat exchangers Compressors System control System behavior in suband trans-critical operation Oil management

20 Summary of work Drafts of computer simulation models have been built for 5 of the system solutions under invistigation Setting up instrumentation (and/or weblink) in field installation are ongoing (9 candidate supermakets, at least 5 are confirmed) Test rig with CO2 as the wroking fluid has been built and will be instrumented and run at EET lab at KTH

21 Ongoing and future tasks Modelling Refine the models by inserting performance curves/data for components used in the real installations Field tests Complete the instrumetnations in the supermarkets Collect and analyze the data Experimental work Install instrumentations on the test rig Test run and draft a detailed experimental plan for discussion with the project partners

22 Thank you! Participating companies: AlfaLaval, Ahlsell, Nibe, IVT, SRM, Danfoss, Green and Cool, RANOTOR, Climacheck, ICA Sverige AB, and Huurre Sweden AB.

23 Transcritical cycle 100 Carbon DioxideTranscritical Cycle c 0, T [ C] e d 0, bar 90 bar 55 bar 0,01 0,063 m3/kg 0 f 35 bar 40 Bar a b 0,2 0,4 0,6 0, s [kj/kg-k]

24 Annual energy consumption Annual Energy Consumption [MWh] Frankfurt Stockholm Phoenix R404A Float 2-St. Prallel NH3/CO2 Cascade 1-St. DX- Centralized 2-St. DX- Centralized Modified Centralized R404A Indirect