Flow behavior of spiral capillary tube for CO 2 transcritical cycle
- PDF / 2,291,198 Bytes
- 12 Pages / 595.276 x 790.866 pts Page_size
- 89 Downloads / 176 Views
Flow behavior of spiral capillary tube for CO2 transcritical cycle Pravin Jadhav1 · Neeraj Agrawal1 Received: 21 October 2019 / Accepted: 10 March 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract A numerical study has been carried out on the spiral capillary tube for the CO2 transcritical cycle. The model is based on the basic principles of conservation of mass, momentum, and energy. The results of this model are validated with earlier published test results. The effect of various geometric parameters like tube diameter, length, roughness, and pitch on the mass flow rate, cooling capacity, and COP has been calculated. The mass flow rate of the tube is mostly influenced by the internal tube diameter, as the diameter increases by 28%, the mass flow increases by 88%. A minor change in mass is observed with a change in pitch and surface roughness, as the pitch increases from 300 to 700 mm, and surface roughness increases by 14%, the mass flow rate and cooling capacity increase only by 2% and 1%, respectively. Similarly, the influence of various operating factors like gas cooler pressure, evaporator temperature, and gas cooler temperature is evaluated. A significant change in mass is observed with the change in gas cooler temperature, as the gas cooler temperature increases by 5%, the mass flow rate, cooling capacity, and COP decrease by 19%, 40%, and 33%, respectively. Relatively less variation in mass flow rate is observed with the change in evaporator temperature. As the evaporator temperature increases by 12%, the mass flow rate decreases by nearly 5.5%, and cooling capacity decreases by 18%. Energy and exergy analyses of a C O2 transcritical system are carried out. Keywords CO2 · Spiral capillary tube · Transcritical · Geometric factor · Operating factor List of symbols A Cross-sectional area of the capillary tube (m2) Q Rate of heat transfer (kW) d Capillary tube diameter (mm) D Coil diameter (mm) √ De Dean number, De = Re d∕D (–) fcs Coiled tube friction factor (–) fst Straight tube friction factor (–) G Refrigerant mass flux (kg m−2 s−1) h Specific enthalpy of refrigerant (kJ kg−1) hfg Latent heat of vaporization (kJ kg−1) L Length of the capillary tube (m) x Mass quality of the refrigerant (–) P Pressure of the refrigerant (bar) p Pitch of the tube (mm) m Refrigerant mass flow rate (kg s−1) T Temperature of the refrigerant (K) * Pravin Jadhav [email protected] Neeraj Agrawal [email protected] 1
Department of Mechanical Engineering, Dr. B. A. Technological University, Lonere, MS 402103, India
R Radius of curvature of the spiral tube (mm) V Velocity of the refrigerant (m s−1) s Specific entropy (kJ kg−1 K−1) i Specific exergy loss (kJ kg−1) Greek symbols 𝜃 Angular displacement (radian) 𝜀 Internal surface roughness (mm) ΔTsub Degree of subcooling (K) 𝜇 Dynamic viscosity (Pa s) 𝜈 Specific volume (m3 kg−1) 𝜌 Density (kg m−3) Subscripts 1–4 The state of the capillary tube cs Single phase with spiral capillary tube g Saturated vapor gc Gas cooler ev Evapo
Data Loading...
