Operational characteristics of a double-spiral heat exchanger for the catalytic incineration of contaminated air

Three-dimensional effects in counterflow heat-recirculating combustors

“…Of course at low Re there is no difference between results with and without the RSM activated for either 2D or 3D simulations; significant differences between simulations without a mechanism for heat transfer enhancement (2D without the RSM activated) and with heat transfer enhancement via the RSM or simulation of Dean vortices begin at Re % 400. Analogous behavior has been observed in spiral counterflow heat exchangers without chemical reaction [24,25]. Figure 6 also shows that the predictions of the 2D and 3D models with the RSM activated are remarkably similar, which indicates that the 2D model of heat transfer and chemical reaction in the X-Y plane coupled to the quasi-1D model of heat losses in the Z-direction used by the 2D model was sufficiently accurate for its purpose.…”

Solutions in closed form for a double-spiral heat exchanger

“…Although not mentioned by him, double-spiral heat exchangers of many turns would appear to have a particular advantage in high-temperature and cryogenic applications in that the external area is reduced to the outer curved surface and the end plates, thereby reducing the leakage of energy to the surroundings. Strenger et al (1990) have examined the use of a double-spiral heat exchanger for the catalytic incineration of low concentrations of contaminates, such as carbon monoxide, hydrocarbons, organic compounds, aerosols, and microorganisms, which may be present in the air of spacecraft, airliner cabins, automobiles, hospital rooms, and industrial clean rooms. In this application the heat losses from a double-pipe heat exchanger would be prohibitive despite the use of the best possible thermal insulation.…”

Scale and geometry effects on heat-recirculating combustors

“…Figure 2b reveals that at small N, E ∼ N as with the linear exchanger, whereas at larger N, even for the adiabatic case E reaches a maximum value then decreases. As discussed by Churchill and collaborators [15,16], this occurs because if N is too large, heat transfer from one outlet channel to the adjoining inlet channel will be too rapid and the temperature of this inlet channel will become hotter than the next-cooler (farther toward the outside of the device) outlet channel and some heat transfer from this inlet channel to the cooler adjacent outlet channel will result, rather than the inlet channel receiving thermal enthalpy from both adjacent outlet channels. This cannot occur with a linear device since heat transfer only occurs from one side of the outlet channel to the adjacent inlet channel.…”