Abstract
An analysis of the dynamic characteristics in an evaporator was numerically performed for control and design of the refrigeration and air conditioning systems. The important factors, such as refrigerant flow rate, inlet enthalpy, inlet air velocity and air temperature, are incorporated with this analysis. An evaporator is modeled for the dynamic characteristics analysis separated into three regions which are the two-phase region, the saturated vapor region and the superheated vapor region. The basic equations of each region were derived in the continuity, heat energy equilibrium and heat transfer equations. The transfer functions of the dynamic characteristics were obtained by the linearization and Laplace transformation. The dynamic response characteristics were evaluated on the Bode diagram with the frequecy response method. These results may be used for the analysis of the dynamic characteristics and design in the total system.
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Abbreviations
- A:
-
Area, (m2)
- Cm :
-
Heat capacity, (J/kg · K)
- H:
-
Enthalpy, (J/kg)
- i :
-
Dimensionless length, (-)
- L:
-
Tube length, (m)
- M:
-
Mass flow rate, (kg/s)
- Q:
-
Heat transfer capacity, (W)
- t:
-
Time, (sec)
- XD :
-
Open area of the expansion valve, (-)
- α:
-
Heat transfer coefficient, (W/m2 · K)
- θ:
-
Temperature, (K)
- ρ:
-
Density, (kg/m3)
- 4:
-
Average of boundary 3∼5
- a:
-
Air or air side
- d:
-
Discharge
- g:
-
Saturated vapor
- i:
-
Inside circumference
- in:
-
Inlet
- m:
-
Tube wall
- o:
-
External circular
- out:
-
Outlet
- r:
-
Refrigerant
- out:
-
Outlet
- s:
-
Superheated vapor
- shm:
-
Average value of internal division
- ─:
-
Average values of integral
- *:
-
Dimensionless
- 0:
-
Steady state
- 1∼6:
-
Each boundary
- 2:
-
Average of boundary 1∼3
References
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Kim, JD., Yoon, JI. & Ku, HG. Dynamic analysis of evaporator characteristics. KSME International Journal 11, 221–228 (1997). https://doi.org/10.1007/BF02944895
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DOI: https://doi.org/10.1007/BF02944895