An experimental study on convective heat transfer performance of steam and air flow in V-shaped rib roughened channels

ABSTRACT

An experimental study on heat transfer characteristics of steam and air flows in a V-shaped ribbed channels was conducted. The effects of Reynolds numbers and rib angles on heat transfer of steam and air were obtained. The area-averaged Nusselt numbers of steam flow at a Reynolds number of 12,000 were 13.9%, 20.6%, 27.1%, and 27.9% higher than those of air flow for rib angles of 90°, 75°, 60°, and 45°, respectively. The correlations for Nusselt number in terms of Reynolds number and rib angle for steam and air in V-shaped ribbed channels were developed.

KEYWORDS:

• Steam cooling
• air cooling
• V-shaped ribbed channel
• gas turbine
• heat transfer

Highlights

• The heat transfer distributions of V-shaped rib-roughness channel cooled by superheated steam and air flows were experimentally investigated.

• Influences of rib angle on heat transfer enhancement of V-shaped ribbed channel under steam and air cooling were both studied.

• Advantage of steam cooling to air cooling in V-shaped ribbed channel with different rib angle was compared and analyzed.

• Correlations for Nusselt number in terms of Reynolds number and rib angle for steam and air cooling in V-shaped ribbed channels were developed.

Nomenclature

A	=	area of the heat plate, m2
AR	=	Aspect ratio of channel
Cp	=	specific heat at constant pressure
Dh	=	hydraulic diameter of the channel, mm
e	=	rib width and rib height, mm
e/Dh	=	relative rib height,
H	=	channel height, mm
h	=	heat transfer coefficient, W/m2/K
I	=	current provided by DC, A
L	=	length of the heat transfer surface, mm
Nu	=	Nusselt number
Nulocal	=	local Nusselt number
Nuave	=	area-averaged Nusselt number
P	=	rib pitch, mm
P/e	=	rib pitch-to-height ratio
Pr	=	Prandtl number
Qloss	=	heat loss dissipating to the environment, W
Qnet	=	heat flux provided by heat plate, W
QT	=	total heating power, W
Re	=	Reynolds number, based on hydraulic diameter of the channel
Tw	=	temperature on target plate, °K
Ts	=	temperature of the coolant in the channel, °K
Tin	=	temperature of the coolant at the inlet, °K
Tout	=	temperature of the coolant at the outlet, °K
U	=	voltage provided by DC, V
V	=	the flow velocity in the channel, m/s
W	=	channel width, mm

Greek symbols

α	=	rib angle, °
λ	=	thermal conductivity, W/(m.K)
μ	=	dynamic viscocity, kg/(m.s)
ρ	=	density, kg/m3

Additional information

Funding

This work was supported by the National Natural Science Foundation of China [51206109].