Numerical Study of Hydrocarbon Charge Reduction Methods in HVAC Heat Exchangers
Abstract
:1. Introduction
2. Tested Systems
2.1. Heat Pump Architectures
2.2. System A—Fin-and-Tube Heat Exchanger
2.3. System B—Brazed Plate Heat Exchangers
3. Simulation Method
3.1. HXSim
3.2. IMST-ART
4. Results and Discussion
4.1. Fin-and-Tube Heat Exchanger Designs
4.2. System Comparison
4.3. Charge
4.4. System Effectiveness
5. Conclusions
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
Nomenclature
Greek | |
Spiral angle | |
Percentage of predicted values with less than 30% error | |
Efficiency | |
Fin angle | |
Roman | |
BPHE | Brazed plate heat exchangers [-] |
COP | Coefficient of Performance [-] |
Fin tip diameter for MF tubes, internal diameter for smooth tube [mm] | |
Outer diameter [mm] | |
EER | Energy Efficiency Ratio [-] |
h | Enthalpy [kJ kg] |
HTC | Heat Transfer Coefficient [kWm K] |
Fin height [mm] | |
m | Refrigerant mass [g] |
n | Number of fins [-] |
p | Pressure [Pa] |
Refrigerants side heat exchange perimeter [m] | |
Q | Capacity [kW] |
q | Heat flux [kWm] |
Heat exchange area ratio of a MF tube to a smooth tube [-] | |
SM | Smooth tube [-] |
T | Temperature [°C] |
Wall thickness [mm] | |
Refrigerants overall heat transfer coefficient [kWm K] | |
W | Power [W] |
x | Vapor quality [-] |
z | Length of tube simulated [m] |
Subscripts | |
Saturated condition |
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Thermal Capacity [kW] | Ambient Dry-Bulb Temperature (Wet-Bulb Temperature) [°C] | Inside Dry-Bulb Temperature (Wet-Bulb Temperature) (System A) [°C] | Water Temperature (System B) [°C] | |
---|---|---|---|---|
Summer | 5 | 35 (24) | 27 (19) | 23/18 |
Winter | 8 | −7 (−8) | 20 (max. 15) | 30/35 |
Unit | Smooth Tube | MF1 | MF2 | |
---|---|---|---|---|
Outer diameter () | 5 | 5 | 5 | |
Internal diameter () | 4.1 | 4.32 | 4.26 | |
Wall thickness () | 0.45 | 0.22 | 0.22 | |
Actual cross sectional area | 13.2 | 15.7 | 14.8 | |
Effective diameter | - | 4.47 | 4.34 | |
Fin height () | - | 0.12 | 0.15 | |
Fin number (n) | [-] | - | 35 | 56 |
Fin angle () | - | 35 | 15 | |
Spiral angle () | - | 15 | 37 | |
Heat exchange area ratio () | [-] | 1 | 1.51 | 2.63 |
Air Side Fin Pitch [mm] | Vertical Tube Pitch [mm] | Fin Thickness [mm] | Air Face Velocity [m s] | |
---|---|---|---|---|
Inside Unit | 2 | 50 | 0.075 | 2 |
Outside Unit | 3.2 | 50 | 0.09 | 5 |
Unit | BPHE1 | BPHE2 | BPHE3 | |
---|---|---|---|---|
Number of Plates | - | 40 | 36 | 40 |
Height | mm | 471 | 324 | 328 |
Width | mm | 81 | 94 | 90 |
Depth per plate | mm | 2.3 | 1.46 | 0.95 |
Inner volume (Refrigrant) | L | 1.0 | 0.53 | 0.33 |
Inner Volume (Secondary Fluid) | L | 1.1 | 0.54 | 0.34 |
Heat transfer area | 1.50 | 0.95 | 0.78 | |
Port Diameter | 20 | 27 | 25 |
Evaporation ( 30%) | Condensation ( 30%) | ||
---|---|---|---|
HTC | Smooth | Liu and Winterton [21] (100) | Dorao and Fernandino [22] (100) |
MF | Rollmann and Spindler [23] (MF1 = 100, MF2 = 66.7) | Cavallini et al. [24] (MF1 = 100, MF2 = 5.4) | |
P | Smooth | Xu and Fang [25] (100) | Xu and Fang [25] (100) |
MF | Diani et al. [26] (100) | Diani et al. [26] (MF1 = 98, MF2 = 100) |
Tube Type | Unit Location | Parallel Circuits (Rows) | Passes in Each Circuit | Total Heat Exchanger Tube Length [m] |
---|---|---|---|---|
Smooth (SM) | Inside unit | 8 | 4 | 33.6 |
Outside Unit | 18 | 4 | 46.8 | |
MF | Inside unit | 9 | 2 | 17.1 |
Outside Unit | 19 | 2 | 22.8 |
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Allymehr, E.; Skaugen, G.; Will, T.; Pardiñas, Á.Á.; Eikevik, T.M.; Hafner, A.; Schnabel, L. Numerical Study of Hydrocarbon Charge Reduction Methods in HVAC Heat Exchangers. Energies 2021, 14, 4480. https://doi.org/10.3390/en14154480
Allymehr E, Skaugen G, Will T, Pardiñas ÁÁ, Eikevik TM, Hafner A, Schnabel L. Numerical Study of Hydrocarbon Charge Reduction Methods in HVAC Heat Exchangers. Energies. 2021; 14(15):4480. https://doi.org/10.3390/en14154480
Chicago/Turabian StyleAllymehr, Ehsan, Geir Skaugen, Torsten Will, Ángel Álvarez Pardiñas, Trygve Magne Eikevik, Armin Hafner, and Lena Schnabel. 2021. "Numerical Study of Hydrocarbon Charge Reduction Methods in HVAC Heat Exchangers" Energies 14, no. 15: 4480. https://doi.org/10.3390/en14154480