Numerical investigation of the temperature distribution inside the cold room with and without duct arrangement

ABSTRACT

Cold rooms are primarily used to preserve food produce in bulk volume. The presence of bulk food produce creates a non-uniformity in cold air flow distribution. This non-uniformity in cold air results in the uneven cooling of the food produce inside the cold room. Furthermore, the ceiling-type cooling units are used in a cold room where the air flow distribution is influenced by the air entrainment effect (generating secondary air flow), resulting in temperature inhomogeneity inside the cold room. An induced duct arrangement is proposed in the present study to suppress the effect of secondary airflow and enhance the cooling uniformity. A numerical investigation of the 3D CFD model of the cold room with an induced duct arrangement is presented in this paper. A cold room of about 81.86 m³ volume is considered. A numerical study is performed for 20 h in transient cooling conditions. Air velocity and temperature are determined at various locations for two different cold room arrangements. It is found that the introduction of a duct arrangement at the rear wall of the cold room reduces the half cooling time by 10% compared to the normal cold room condition due to the elimination of the entrainment of air. The convective heat transfer coefficient is seen to be increased by 12.7% compared to the normal cold room, while the temperature inhomogeneity inside the room decreases by 14.3% with the introduction of duct arrangement.

KEYWORDS:

• Cold room
• CFD
• induced duct
• temperature inhomogeneity
• air flow field

Disclosure statement

No potential conflict of interest was reported by the author(s).

Nomenclature

$F_1$$F_2$	=	Blending functions
$C_s$	=	Coefficient of swirl
$h_{cv}$	=	Convective heat transfer coefficient
$C{D}_{kw}$	=	Cross diffusion term
$Y$	=	Dimensionless temperature parameter
$C_1,C_2,C_3$	=	Experimental coefficients for the fan curve equation
$P$	=	Pressure
$P_k$	=	Production limiter
$R$	=	Radius
$RH$	=	Relative humidity
$q_{apple-air}$	=	Respiration heat of apple
$Cp$	=	Specific heat capacity
$T$	=	Temperature
$t$	=	Time
$k$	=	Turbulence kinetic energy
$\underset{t}{Pr}$	=	Turbulent Prandtl number
$V$	=	Velocity
$u$	=	Velocity component in x direction

Greek symbols

${\omega }^{\prime }$	=	Angular velocity
$\rho$	=	Density
$\mu$	=	Dynamic viscosity
${\nu }_t$	=	Kinematic eddy viscosity
$\nu$	=	Kinematic viscosity
$\omega$	=	Specific dissipation of turbulence kinetic energy
$\sigma$	=	Temperature inhomogeneity
$\lambda$	=	Thermal conductivity
${\sigma }_k$${\sigma }_{\omega }$	=	Turbulence model constants
$a_1$$\alpha$$\beta$${\beta }^{\ast }$	=	Turbulence model constants
${\lambda }_{eff}$	=	Turbulent thermal conductivity

Subscripts

$air$	=	air
$a$	=	apple
$block$	=	apple bin
$axial$	=	axial
$d$	=	duct
$f$	=	fluid
$in$	=	initial
$max$	=	maximum
$min$	=	minimum
$tangential$	=	tangential

Additional information

Funding

The work was supported by the Science and Engineering Research Board [EMR/2016/007289]