Effect of circular inside conical ring obstacles on heat transfer and friction characteristics of round jets impingement solar air rectangular passage

ABSTRACT

Turbulent convection of fluid flow through the impingement round jets solar air rectangular passage with circular inside conical ring obstacle shapes is studied experimentally. The testing of a rectangular solar air passage with round impinging jet contains; relative inside conical ring height ($H_R/D_H)$ lies from 0.073–0.128, ratio of inlet flow diameter to inner print diameter of ring ($D_{IR}/D_{BR})$ lies from 1.3–2.3, ratio of ring diameter to ring height $(D_O$/$H_R)$ lies from 1.67–2.67, relative X-axis pitch ($X_S/D_O)$ lies from 4.71–7.71, relative Y-axis pitch ($Y_S/D_O)$ lies from 2.92–5.14, relative impingement round jets diameter ($D_{IJ}/D_H)$ and Reynolds number (Re) of flow was varied between 5,000 to 23,000. The fixed values of relative impingement round jets diameter ($D_{IJ}/D_H)$ of 0.366, relative X-axis jet distance ($X_{imp}/D_H)$ of 0.366, and relative Y-axis jet distance ($Y_{imp}/D_H)$ of 0.311 were selected. The highest value of hydrodynamic and thermal performance is observed at $H_R/D_H$ of 0.110, $D_{IR}/D_{BR}$ of 1.7, $D_O$/$H_R$of 2.33, $X_S/D_O$of 5.28, $Y_S/D_O$of 3.42, $D_{IJ}/D_H$ of 0.055, $X_{imp}/D_H$of 0.366, and $Y_{imp}/D_H$ of 0.311.

KEYWORDS:

• Solar energy
• conical ring
• impingement round jets
• hydrodynamic performance
• heat transfer

Nomenclature

$A_{ap}$	=	Area of intense heated wall(m2)
$A_F$	=	Area of flow (m2)
$A_{OM}$	=	Area of orifice meter (m2)
$C_{do}$	=	Coefficient of discharge of orifice meter
$C_{ha}$	=	Specific heat of air (J/kg K)
$D_{BR}$	=	Inner print base diameter of inside conical ring (m)
$D_H$	=	Hydraulic diameter of impingement round jets solar air collector (m)
$D_{IJ}$	=	Impingement round jets diameter (m)
$D_{IJ}/D_H$	=	Relative impingement round jets diameter
$D_{IR}$	=	Inlet flow diameter of inside conical ring (m)
$D_{IR}/D_{BR}$	=	Ratio of inlet flow diameter to inner print diameter of ring
$D_O$	=	Outer diameter of inside conical ring (m)
$D_O$/$H_R$	=	Ratio of ring diameter to ring height
$d_o$	=	Diameter of orifice meter (m)
$f$	=	Friction factor
$f_{os}$	=	Friction factor with roughness shape
$f_{ss}$	=	Friction factor for smooth wall
$H_R$	=	Height of inside conical ring or obstacle (m)
$H_R/D_H$	=	Relative inside conical ring height
$H_{ap}$	=	Height of air passage (m)
$h_c$	=	Heat transfer coefficient (W/m2 K)
$K_c$	=	Thermal conductivity (W/m K)
$L_{ap}$	=	Length of air passage (m)
$m_{FA}$	=	Mass flow rate of air (kg/s)
$N$	=	Number of thermocouples
$Nu$	=	Nusselt Number
$N{u}_{os}$	=	Nusselt number for obstacle wall
$N{u}_{ss}$	=	Nusselt number for smooth wall
$P_{ar}$	=	Air pressure (Pa)
$(\mathrm{\Delta }{\hspace{0.17em}}_{PD}{)}_o$	=	Pressure drop across the orifice (Pa)
$\mathrm{\Delta }{\hspace{0.17em}}_{PD}$	=	Pressure drop across the test section (Pa)
$Q_{hg}$	=	Heat transfer from heated wall to the flowing air (W)
$Re$	=	Reynolds number
$R_g$	=	Specific gas constant for dry air (287.05 J/kg K)
SAH	=	Solar air heater
$T_{in}$	=	Bulk mean temperature of air at inlet (K)
$T_{out}$	=	Bulk mean temperature of air at outlet (K)
$T_p$	=	Plate temperature of air (K)
$T_{sa}$	=	Standard air temperature (K)
$V_{ar}$	=	Velocity of air (m/s)
$W_{ap}$	=	Width of air passage (m)
$X_S$	=	X-axis direction pitch of inside conical ring (m)
$X_S/D_O$	=	Relative X-axis pitch of inside conical ring
$X_{imp}$	=	X-axis pitch distance between impingement round jets (m)
$X_{imp}/D_H$	=	Relative X-axis jet distance
$Y_S$	=	Y-axis direction pitch of inside conical ring (m)
$Y_S/D_O$	=	Relative Y-axis pitch of inside conical ring
$Y_{imp}$	=	Y-axis pitch distance between impingement round jetss (m)
$Y_{imp}/D_H$	=	Relative Y-axis jet distance
$Z$	=	Jet to target plate spacing (m)

Greek symbols

${\beta }_{OP}$	=	Ratio of orifice meter to pipe diameter (dimensionless)
${\eta }_{per}$	=	Thermo-hydraulic performance (dimensionless)
${\rho }_{ar}$	=	Density measurement of air (kg/m3)
$\mu$	=	Dynamic viscosity of air (kg/m.s)
$\upsilon$	=	Kinematic viscosity of air (m2/s)

Subscripts

ap	=	Heated wall
ar	=	air
FA	=	Flow rate of air
H	=	Hydraulic
IJ	=	Impingement round jets
imp	=	Impingement
in	=	In
OM	=	Orifice meter
OP	=	Orifice to pipe
OS	=	Obstacle wall
out	=	Out
p	=	plate
per	=	performance
R	=	Ring or obstacle
sa	=	Standard air
SS	=	Smooth wall