JPS6346391A - Fluidized bed heat exchanger - Google Patents

Abstract

PURPOSE:To reduce pressure loss and to obtain a high heat transfer coefficient by specifying the ratio of the fin interval of a heat exchanger or the tube interval thereof with respect to the diameter of fluidized particles. CONSTITUTION:In a fluidized bed heat exchange in which around a heat exchanger formed by bonding a plurality of flat tubes 3 through which a coolant flows and a plurality of fins 2 by brazing or tube expansion, fluidized particles 1 are retained, the ratio of the fin interval or the tube interval with respect to the diameter of said fluidized particles is made three times or more. By this arrangement, the fluidized particles 1 can be stably caused to float within a temperature interface layer formed along the air flow direction on the surfaces of fins 2 or tubes 3, and hence frosting can be extremely delayed. Accordingly, pressure loss of the heat exchanger can be reduced and the heat transfer coefficient can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fluidized bed heat exchanger that can be widely used for air conditioning, heat pumps, industrial heat exchangers, and the like.

[Conventional technology]

Fluidized bed heat exchangers have conventionally been widely used for chemical plants or waste heat recovery, but these generally have a high density of fluidized particles (ρρ≠3000Kqm/m').
The particle size is small, less than 0.3φ, so the pressure loss is 10
Large pressure loss of 0+a+Aq or more, 5+l1lII
The reality is that it is not used in low pressure drop type heat exchangers such as Aq heat exchangers for heat pumps.

[Problem that the invention seeks to solve]

When used as a low pressure drop type such as a fluidized bed heat exchanger for a heat pump, there is a minimum fin spacing or tube spacing that allows particles to be stably suspended between the fins or tubes of the heat exchanger when the diameter of the fluidized particles is determined.

That is, there is an optimum value for improving the heat transfer coefficient with low pressure drop by stably suspending the fluidized particles.

The present invention aims to provide a fluidized bed heat exchanger that can obtain a high heat transfer coefficient with a low pressure drop necessary for a low pressure drop type heat exchanger such as a heat exchanger for a heat pump.

[Failure to solve problems]

In order to achieve the above object, the present invention provides a fluidized bed heat exchanger in which fluidized particles are held around the heat exchanger. The fluidized bed heat exchanger is configured with a ratio of 3 times or more.

[Effect]

By setting the fin spacing or tube spacing to three times or more the diameter of the fluidized particles as described above.

Fluid particles can be stably suspended in a temperature boundary layer formed along the air flow direction on the fin or tube surface.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows a fluidized bed heat exchanger in which a plurality of flat tubes 3 through which a refrigerant (Freon 22 or 12) flows and a plurality of fins 2 are joined by brazing or tube expansion.

FIG. 2 shows a fluidized bed heat exchanger consisting only of a plurality of flat cheeps 3. 1 is a fluid particle, 2 is a plate fin,
3 is a flat tube, 4 is a distribution plate, S is a plate fin 2
or the minimum dimension between the flat tubes 3. Note 2
Although not shown, a round chip is used instead of the flat chip 3.
The present invention can be similarly applied to a heat exchanger using a fin or a heat exchanger using a corrugated fin.

Further, better results can be obtained by arranging the tubes in a staggered arrangement with respect to the air flow a, as shown in Figure 9.

b indicates the flow of refrigerant.

FIG. 3 is a diagram showing the relationship between the ratio of the fin spacing to the particle diameter (S/particle diameter) and the heat transfer coefficient of the heat exchanger, and shows the relationship between the ratio of the fin spacing to the particle diameter (S/particle diameter) and the heat transfer coefficient of the heat exchanger. The heat transfer coefficient decreases rapidly in O, but this is because the drag force of the air flow acting on the particles is balanced with the gravity of the particles, so the number of particles that can exist between the pitches decreases rapidly, and the heat transfer rate decreases rapidly. The number of particles colliding with the surface is reduced and frost formation is accelerated. However, if S/particle size>3.0 is selected, this problem will not occur and frost formation can be delayed to the coffin ends.

Figure 4 shows the relationship between heat transfer coefficient/pressure drop: kW/△Pa and particle diameter: dp in a fluidized bed heat exchanger with a predetermined pitch, using particle density: ρp as a parameter, which is the optimum value for fluidizing the particles. The heat transfer coefficient and pressure loss are experimental results. The fluidized particles used in the experiment were polystyrene foam particles or equivalent particles, and ρp = 500 ~ l O00 (Kym/i)
It is. In addition, as a heat exchanger for a heat pump, kW/
Since ΔPa=40 (k, Il/−−℃/pharyngeal AQ) or more is required, when p=500, dp=1.
When 2ρp=1000 is 5 or less, dp==Q, and a particle size of 3 or less is appropriate.

〔Effect of the invention〕

As described above, according to the present invention, by setting the fin spacing or tube spacing to three times or more the diameter of the fluidized particles, it is possible to reduce the pressure drop in the heat exchanger and improve the heat transfer coefficient.

[Brief explanation of the drawing]

Figure 1 is a block diagram of a plate-fin fluidized bed heat exchanger, Figure 2
The figure shows the configuration of a flat cheap fluidized bed heat exchanger, Figure 3 shows the heat transfer characteristics of the fluidized bed heat exchanger, and Figure 4 shows the relationship between fluid particle diameter and heat transfer coefficient/pressure loss. be. 1...Fluid particles, 2...Plate fins, 3...
Flat tube, 4... Dispersion plate, S... Fin spacing or tube spacing

Claims (1)

[Claims] A fluidized bed heat exchanger comprising fluidized particles held around the heat exchanger, characterized in that the ratio of the fin spacing or tube spacing of the heat exchanger to the diameter of the fluidized particles is three times or more. Fluidized bed heat exchanger.