Heat Transfer From Arrays of Impinging Jets with Large Jet-to-Jet Spacing

Abstract

Local and average convective heat transfer coefficients were measured for arrays of widely spaced impinging air jets and correlated in terms of system geometry, air flow, and fluid properties. The configurations were square arrays of circular turbulent jets (spaced from 10–25 diameters apart) incident upon a flat isothermal target surface. Independent parameters were varied over ranges generally corresponding to gas turbine cooling applications. Local heat transfer coefficients were influenced by interference from neighboring jets only when the target plate and the jet orifice plate were less than five jet diameters apart. Average heat transfer coefficients were nearly equal for all the arrays tested as long as the coolant flow per unit area of target surface was held constant. In fact, there was a tendency for the more widely spaced configurations to produce slightly higher average heat transfer under such conditions.

Optimum Jet-to-Plate Spacing of Inline Impingement Heat Transfer for Different Crossflow Schemes

“…Hollworth and Berry [2] measured the heat transfer values for impinging jet arrays with large jet-to-jet spacings, which are X/d ¼ 10, 15, 20, and 25. They found that the local heat transfer coefficients are influenced by interference from neighboring jets and the averaged heat transfer coefficient is sensitive to jet-toplate spacing only when the jet-to-jet spacing is less than five jet diameters.…”

The study of flow and heat transfer characteristics of impinging jet array mounting air-induced duct

“…Generally, Nusselt number distributions for the case of S/d=6 were higher than the case of S/d=8. This is from the effect of interference of adjacent jets for the case of smaller jet-to-jet distance resulting on increasing turbulence intensity of jet before impingement as mentioned in previous work [25]. For the case of jet with air-induced duct for both S/d=6 and 8, areas of high Nusselt number around impingement regions were larger than those for conventional jets.…”

Heat transfer and wall pressure characteristics of a twin premixed butane/air flame jets

“…Both single and multiple jets are used for different purposes. A single jet is usually employed to produce localized heating or cooling [1,2]. In many applications, a large surface area is required to be heated or cooled, or enhancement of global heat transfer is needed, such as in water heaters, domestic gas stoves and the thrust-augmenting ejectors for VTOL/STOL aircraft, thus, it is necessary to apply multiple-jet system [1][2][3][4].…”

“…A single jet is usually employed to produce localized heating or cooling [1,2]. In many applications, a large surface area is required to be heated or cooled, or enhancement of global heat transfer is needed, such as in water heaters, domestic gas stoves and the thrust-augmenting ejectors for VTOL/STOL aircraft, thus, it is necessary to apply multiple-jet system [1][2][3][4]. Using information for a single jet to design a multiple-jet system is usually not valid, because of the strong interaction between the jets, except when the jets are widely spaced, so that no interaction can be reasonably assumed [5].…”