Heat transfer and pressure drop measurement in wavy channels with flow disturbers

Conference · Thu Jul 01 04:00:00 EDT 1999

OSTI ID:20030445

Dini, S; Veronesi, R; Hryniewicz, E V

In the current work, the transient method was employed to obtain the local heat transfer coefficient for a 6 in. x 3/8 in. x 12 in. (15.24cm x .9525cm x 30.48cm) Plexiglas {reg_sign} wavy channel with and without flow disturbers. A short duration transient test was performed to measure the heat transfer coefficient by introducing heated air over test specimen that had been sprayed with calibrated thermochromic liquid crystals. This technique allowed the experimenter to observe the temperature changes using a video camera. because a Plexiglas surface has a low thermal diffusivity, a one-dimensional assumption is a reasonable approximation because the surface temperature response is limited to a thin layer near the surface and lateral conduction is small. The heat transfer coefficient using the transient technique is then determined from the response of the surface temperature to a step change in the local temperature. Using this method, the axial variation in the heat transfer coefficient for Reynolds numbers in the laminar (1100) and turbulent region (2900) were obtained. These Reynolds numbers were based on the hydraulic diameter at the inlet of the wavy channel. Also, in this investigation, the region of greatest heat transfer and the pressure drop were both experimentally and analytically determined and the friction factor across an in-phase corrugated wall channel (wavy channel) at Reynolds numbers of 1100 and 2900 were obtained. A manometer and a pressure transducer were employed to measure pressure drop across the channel. The effect of flow disturbers mounted on each peak, alternate peaks and the first six peaks of a twelve-peak channel were also investigated. For all cases, the pressure drop and friction factor were shown to moderately increase with rib placement in the test section when compared to the results obtained from a similar smooth wavy channel without ribs. Additionally, for all cases, the friction factor also decreased with an increase in the Reynolds number. If the ratio of pumping power to heat transfer rate was selected as the primary criteria, the channel with a flow disturber placed on alternate peaks was determined to be the best configuration. The following figure illustrates the color changes of the liquid crystals.

• Research Organization: Western New England Coll., Springfield, MA (US)
• OSTI ID: 20030445
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
AUGMENTATION
BAFFLES
FLUID FLOW
FRICTION FACTOR
HEAT TRANSFER
PRESSURE DROP