View
2
Download
0
Category
Preview:
Citation preview
Laboratórios de Pesquisa em Refrigeração e TermofísicaResearch Laboratories for Emerging Technologies in Cooling and Thermophysics
A NTU-Based Model to Estimate SuctionSuperheating in Scroll Compressors
Marco C. DINIZ and Cesar J. DESCHAMPSFederal University of Santa Catarina
22nd International Compressor Engineering Conference
International Compressor Engineering Conference 2014
Summary
1. Introduction/Motivation
2. Compression process model
3. Thermal model
4. Results
5. Conclusions
International Compressor Engineering Conference 2014
Scroll compressors
• Compression process:- Performed by two identical scrolls;- Occurs from outer to central region;- Continuous;- Few moving parts;
• Important characteristics:- Low noise and vibration;- High efficiency and reliability;- Easy modulation of capacity;
International Compressor Engineering Conference 2014
Heat transfer inefficiencies
• Loss of performance:- Suction superheating;- Compression chamber
superheating;
• Reliability:- Discharge temperature;
TSUC > TIN
International Compressor Engineering Conference 2014
Objectives
Develop a model to predict suction superheating in scrollcompressors:
- Couple to a compression process model;
Evaluate its versatility:- Test the model in two compressor with different refrigerants;
International Compressor Engineering Conference 2014
Compression process model
• Developed by Pereira (2012);
• Main characteristics:- Calculation of geometric parameters;- Transient lumped conservation
equations;- Leakage and heat transfer correlations
were developed;- Requires a certain number of cycles to
achieve convergence;
• Interaction with thermal model- Receives Tsuc;- Returns mass flux, heat transfer and
indicated power;
Tsuc
International Compressor Engineering Conference 2014
Thermal model
• Existing thermal models:- Usually experimentally calibrated;- Only applicable to specific compressors and operating conditions;- Cannot be used as project tools;
• This work proposes:- Simplified thermal model;- No experimental calibration;- Based on Winandy et al. (2002) model;
• Winandy et al. (2002):- Sequence of steps to represent the phenomena inside the compressor;- Employs an isothermal fictitious surface;- Uses experimental data for calibration;- Was successfully used and improved by other authors (Cuevas et al., 2009
and Duprez et al., 2010);
International Compressor Engineering Conference 2014
Thermal model: simplification
M ot or M ot or
m cpin
m cpsuc
m cpout
m cpdis
m cpsuc
Qsuc
Qsuc
Qsuc
Qsuc
QdisEx t ernal A m bient
C om pression cham ber
D ischarge plenum
Oil
Shell
Suct ionplenum
Suct ion plenum
Suct ionplenum
Suct ionplenum
Qchm
Qam b
Qchm
Qsuc
Suction Environment
Compression Chamber
Discharge Environment
Qdis
ṁcpin ṁcpsuc
Tw
ṁcpdis ṁcpout
Tw
Tw
Qamb
Qeml
(Thermal Model) (Thermal Model)(Compression cycle model)
Real geometry
Simplified flow approach
International Compressor Engineering Conference 2014
Thermal model: equations
Qchm
Qsuc
Suction Environment
Compression Chamber
Discharge Environment
Qdis
ṁcpin ṁcpsuc
Tw
ṁcpdis ṁcpout
Tw
Tw
Qamb
Qeml
(Thermal Model) (Thermal Model)(Compression cycle model)
International Compressor Engineering Conference 2014
Thermal model: equations
Qchm
Qsuc
Suction Environment
Compression Chamber
Discharge Environment
Qdis
ṁcpin ṁcpsuc
Tw
ṁcpdis ṁcpout
Tw
Tw
Qamb
Qeml
(Thermal Model) (Thermal Model)(Compression cycle model)
International Compressor Engineering Conference 2014
Thermal model: equations
Qchm
Qsuc
Suction Environment
Compression Chamber
Discharge Environment
Qdis
ṁcpin ṁcpsuc
Tw
ṁcpdis ṁcpout
Tw
Tw
Qamb
Qeml
(Thermal Model) (Thermal Model)(Compression cycle model)
From compression processmodel
International Compressor Engineering Conference 2014
Thermal model: equations
Qchm
Qsuc
Suction Environment
Compression Chamber
Discharge Environment
Qdis
ṁcpin ṁcpsuc
Tw
ṁcpdis ṁcpout
Tw
Tw
Qamb
Qeml
(Thermal Model) (Thermal Model)(Compression cycle model)
International Compressor Engineering Conference 2014
Thermal model: equations
Qchm
Qsuc
Suction Environment
Compression Chamber
Discharge Environment
Qdis
ṁcpin ṁcpsuc
Tw
ṁcpdis ṁcpout
Tw
Tw
Qamb
Qeml
(Thermal Model) (Thermal Model)(Compression cycle model)
International Compressor Engineering Conference 2014
Thermal model: equations
Qchm
Qsuc
Suction Environment
Compression Chamber
Discharge Environment
Qdis
ṁcpin ṁcpsuc
Tw
ṁcpdis ṁcpout
Tw
Tw
Qamb
Qeml
(Thermal Model) (Thermal Model)(Compression cycle model)
International Compressor Engineering Conference 2014
Thermal model: equations
Qchm
Qsuc
Suction Environment
Compression Chamber
Discharge Environment
Qdis
ṁcpin ṁcpsuc
Tw
ṁcpdis ṁcpout
Tw
Tw
Qamb
Qeml
(Thermal Model) (Thermal Model)(Compression cycle model)
International Compressor Engineering Conference 2014
Thermal model: equations
Qchm
Qsuc
Suction Environment
Compression Chamber
Discharge Environment
Qdis
ṁcpin ṁcpsuc
Tw
ṁcpdis ṁcpout
Tw
Tw
Qamb
Qeml
(Thermal Model) (Thermal Model)(Compression cycle model)
International Compressor Engineering Conference 2014
Thermal model: equations
Qchm
Qsuc
Suction Environment
Compression Chamber
Discharge Environment
Qdis
ṁcpin ṁcpsuc
Tw
ṁcpdis ṁcpout
Tw
Tw
Qamb
Qeml
(Thermal Model) (Thermal Model)(Compression cycle model)
International Compressor Engineering Conference 2014
Thermal model: equations
Qchm
Qsuc
Suction Environment
Compression Chamber
Discharge Environment
Qdis
ṁcpin ṁcpsuc
Tw
ṁcpdis ṁcpout
Tw
Tw
Qamb
Qeml
(Thermal Model) (Thermal Model)(Compression cycle model)
International Compressor Engineering Conference 2014
Thermal model: chart
International Compressor Engineering Conference 2014
Thermal model: chart
International Compressor Engineering Conference 2014
Thermal model: chart
International Compressor Engineering Conference 2014
Thermal model: chart
International Compressor Engineering Conference 2014
Thermal model: chart
International Compressor Engineering Conference 2014
Complete model solution
International Compressor Engineering Conference 2014
Results: compressors A and B
Compressor A
Compressor B
International Compressor Engineering Conference 2014
Results: compressors A and B
Compressor A
Compressor B
International Compressor Engineering Conference 2014
hsuc hdis
• When hsuc increases, suction temperature also increases.
• hdis influences more thesuction temperature;
Tsu
c[o C
]
1/8 1/4 1/2 1 2 4 820
25
30
35
40
45
50
55
60
AHRI-AAHRI-GAHRI-D
10000 rpm
Tsu
c[o C
]1/8 1/4 1/2 1 2 4 8
30
35
40
45
50
55
60
65
70
AHRI-AAHRI-GAHRI-D
10000 rpm
Results: hsuc and hdis variation
International Compressor Engineering Conference 2014
Results: operating conditions variation
• Suction temperature increase with pressure ratio is more noticed at lower evaporation temperatures and lower speeds;
Tc [oC]
Tsu
c[o C
]
25 30 35 40 45 50 55 60 6530
35
40
45
50
55
6000 rpm8000 rpm10000 rpm
Te = -1.1 oC
Tc [oC]
Tsu
c[o C
]
25 30 35 40 45 50 55 60 6530
35
40
45
50
55
6000 rpm8000 rpm10000 rpm
Te = 7.2 oC
International Compressor Engineering Conference 2014
Conclusions
• Coupled solution:- Allows a comprehensive simulation of compressor performance;- Simple thermal model;- No experimental calibration;
• Two different compressors;- Good estimation for suction temperature;- Not so good estimation for outlet temperature;- More heat transfer coefficients should be tested;
• Sensitivity analysis:- Physically consistent behavior;- Allows the estimation of efficiencies;
International Compressor Engineering Conference 2014
Acknowledgements
The present investigation is part of a cooperation agreement between the Federal University of Santa Catarina (UFSC) and EMBRACO.
Support from the Brazilian Funding Agencies FINEP and CAPES is also appreciated.
Slide 31 de 51Conclusões
Laboratórios de Pesquisa em Refrigeração e TermofísicaResearch Laboratories for Emerging Technologies in Cooling and Thermophysics
Cláudio Melo melo@polo.ufsc.br
Federal University of Santa CatarinaDepartment of Mechanical Engineering
88040-900 – Florianópolis – SC - Brazil phone +55 (48) 3234.2691 fax +55 (48) 3234.5166
http://www.polo.ufsc.br
Laboratórios de Pesquisa em Refrigeração e TermofísicaResearch Laboratories for Emerging Technologies in Cooling and Thermophysics
marcodiniz@polo.ufsc.br
Thank you!
Recommended