TH46407A - Method for determining the length of capillary pipes used in air conditioning and cooling systems - Google Patents

Abstract

DC60 This method for determining the length of capillary pipes used in air conditioning and refrigeration systems is based on Principles of fluid mechanics, thermodynamics. And numerical method which can be applied to refrigeration systems that use all types of refrigerants currently available. This method of determining the length of the capillary pipes used in air conditioning and refrigeration systems is based on Principles of fluid mechanics, thermodynamics. And numerical method which can be applied to refrigeration systems that use all types of refrigerants currently available.

Claims (1)

1. Method for determining the length of capillary pipes used in air conditioning and refrigeration systems, with a procedure that consists of It divides the flow phase into two parts, one state flow and two state flow, and uses the fluid mechanics equation and the energy conservation equation. In the analysis of Refrigerant flow inside capillary tubes It is characterized by - the division of the two flow states into smaller intervals to calculate the capillary tube length is divided by assigning each pressure equal to each interval.- Determination of vapor quality (x ) In each small period Using Equation 8 x = {-hfg-G2vfvfg + ((hfg + G2vfvfg) 2-2 (G2vfg2) (hf + 0.5G2vf2-h1)] 0.5) G2vfg2, where G is the mass flow rate per sectional area. Hf is the enthalpy of refrigerant in liquid state, hf is the refrigerant enthalpy in gaseous state, hl is the enthalpy at the position before entering the capillary vf. Is the specific volume of the refrigerant in the liquid state, vg is the specific volume of the refrigerant in the gaseous state - using the equation to find the value Mu, herein is the suitability - use the Ciechitti equation (Equation 12b ) As R134a refrigerant, Mu tp = xMu g + (1-x) Mu l, where Mu tp is the refrigerant's kinetic viscosity in the two flow states, Muf is the kinetic viscosity of the refrigerant. Cool in the liquid state, Mug is the kinetic viscosity of the refrigerant in the gaseous state - use Dukler's equation (Equation 12 c) when refrigerant R12 and R22 Mu tp = (xv g Mu g + (1 -x) vf Mu f) xv g + (1-x) vf - Use McAdams's equation (Equation 12 d) as other refrigerants 1 = x + 1-x Mu tp Mu g Mu f - Finding the f-number in a small range is a two-state flow. Assigned to think as a single state without multipliers. Which here uses the equation of Colebrook (Equation 6) or Churchill (Equation 7) 1 = 1.14 - 2 log [epsilon + 9.3] (formula) fd Re (formula) ff = 8 ((8) 12 + 1) 1/12 (Re ) (B + C) 3/2 where B = (2.457 In (1)) 16 and C = (37530) 16 (7) 0.9 + 0.27 epsilon Re Re d where d is the inner diameter of the pipe, f is the friction factor. Re is the Reynolds number, epsilon is the roughness of the pipe surface - calculating the length of the capillary tube during the two-state flow (Ltp) using Equation 10 L tp =. d [-2 P a max, P evap (formula) p dp + 2 P x max, P evap (formula) dp] G2 P3 f tp P3 pf tp, where ftp is the friction factor in the two-state flow P. Where is the refrigerant pressure; P3 is the pressure at the single-stage end-of-flow and the dual-stage flow is initiated; P is the refrigerant density. The calculated capillary tube length must not cause a blocked flow phenomenon when entropy is highest. Consider the pressure (P) with the pressure at the evaporator (Pevap) .If P at this position is higher than Pevap, P4 = P, but if P at this position is less than Pevap, P4 = Pevap.