FR2666474A1 - DEVICE FOR HEATING FLUIDS BY JOUL EFFECT. - Google Patents

Abstract

The invention relates to a device for heating a fluid comprising a pipe (1) in which the fluid circulates. This pipe (1) comprises at least one rectilinear electrically conductive portion (1a) traversed by an electric current causing it to heat up by the Joule effect and therefore to heat up the fluid. This device comprises supply flanges (4) which can be fixed in an adjustable manner along this rectilinear portion (la) so as to be able to vary, for a given supply power, the specific power dissipated by the pipe (1). depending on the distance separating these supply flanges (4).

Description

1 -

  DEVICE FOR HEATING FLUIDS

BY JOULE EFFECT

  The present invention relates to the heating of fluids by the Joule effect and relates more particularly to a device for heating a fluid circulating in

a tube heated by the Joule effect.

  In these heating devices, it is an electric current circulating in the tube which heats it by effect

  Joule, and the tube heats the fluid, usually a li-

  quide or a pasty fluid which circulates there, by conduction

and / or radiation.

  Such a device comprises a set of tubes in one

  thermally conductive material with electrical resistivity

  specific stick, helically shaped, serpentine, or com-

  taking straight parts connected by elbows.

  To obtain a uniform heating of the fluid, it is disadvantageous to use the Joule effect in the bent portion of the tube, because at this location its thickness is

  not constant and the electric currents do not repair

  do not weave uniformly in the section of the tube causing an inhomogeneous heating of the tube and therefore of the fluid which

circulates there.

  To overcome this drawback, the document FR-Ai-

  2632475 proposes to short-circuit the curved parts of the tube so as to pass the heating current only

in its straight portions.

  All of these devices, however, have the drawback

  negate the need for electrical power supplies

  2 - plate with complicated regulation and acting on a large range of current values, since it is this only parameter which makes it possible to regulate the quantity of energy delivered to the fluid. The present invention relates to a heating device of a fluid circulating in a rectilinear part

  of tube allowing a simple regulation of the delivered energy and especially to modify for a given transferred energy the density of energy delivered per unit area10 of the tube.

  This is particularly necessary for the heating of heat-sensitive fluids or liquids such as liquids.

  quides and pasta for the treatment of which any local overheating can cause degradations

organoleptics in particular.

  The device for heating a fluid comprising at least one rectilinear portion of electrically conductive tube inside which the fluid circulates and which is crossed by an electric current causing it to heat up by Joule effect and consequently the heating of the fluid is characterized by the fact that it includes

  current supply flanges on this rectilinear portion of the pipe displaceable relative to the latter so as to vary, for a given current, the energy density dissipated by the pipe as a function of the distance separating these flanges.

  The attached drawing illustrates schematically and by way of example an embodiment of the heating device

according to the invention.

  3 - Figure 1 illustrates schematically and in section an electrically conductive pipe intended to convey a

  fluid provided with supply flanges supplied with electric current by a low voltage transformer and a regulator

reader.

  Figures 2 and 3 are views of a supply flange

  tation. In the example illustrated diagrammatically by way of example, the heating device comprises a pipe 1 serving for the circulation of the fluid to be heated This pipe is intended to be connected at its upstream end to a supply of said fluid and at its downstream end to a circuit for its use or storage. This pipe 1 has at least one straight portion

  la, three in the example illustrated, consisting of a material

  riau conductor of electricity and having a resistance

  determined activity, as homogeneous as possible. In the example illustrated, the entire pipe 1 is made of an electrically conductive material, but according to a

  alternatively the bends 2, 3 could be made of an electrically insulating material.

  This Joule effect heating device also comprises, for each rectilinear part 1a of the pipe 1, two flanges for supplying electric current 4 Each flange 425 is formed by two half-shells 4 a, 4 b enclosing the pipe 1 and clamped l 'one against the other and against said pipe 1 using screws or studs and nuts 5,6 These supply flanges 4 can thus be fixed on the tube at any point of its rectilinear portions, this which allows you to vary the distance between two flanges 4-

  fixed on the same straight portion and therefore the resistance

  tance measured across these two flanges.

  This allows for a given supply current, therefore a given supply power, to vary the specific power, that is to say the power per square centimeter of exchange surface between the pipe 1 and the fluid. This is very important, because it is therefore possible to modify this specific power without modifying the

  total power of the device and therefore its supply current, according to the specific characteristics of the

  what to treat, and in particular to avoid any local overheating of the fluid. In the example illustrated, each of the three pairs of supply flanges associated with the straight portions of pipes is connected to a phase of a three-phase supply. In addition, the adjacent rings of two neighboring pairs, located on either side of the pipe. '' a bend 2, are electrically connected. 20 The electrical supply of the heating device is done from the three-phase distribution network, by

  example via a low voltage transformer

  7 (39 Volts) and a semi-static 8 switch

  conductor such as controlled thyristors 9.

  The semiconductor switch control is

  produced by an electronic device comprising a

  regulator 10 for example of the type existing in the trade "Thermophonix 96 No 11877" whose output controls the

  conduction or shutdown of the thyristor (s) via

  diary of an ignition modulator causing the change - state of the thyristor only at zero crossings of the

  alternating supply current to avoid over-voltage during switching.

  The regulator 10 is controlled by the output signal of a temperature detector 11 plunging into the current

  of the fluid downstream of the heating part of the pipe 1.

  The supply of the pipe 1, and therefore its production of heat is controlled directly by the temperature of the fluid, very precisely to a few tenths of a degree

centigrade close.

  The electric power delivered to the pipe 1 is regulated by all or nothing and can vary between O and 100% according to the time of conduction of the thyristors This manner of proceeding allows to obtain a great precision of the regulation of the temperature of the fluid, of avoid overheating

  this one and have a very short response time.

  This static regulation mode is described for example in patent CH-A-649,827 Of course any other

  mentation regulated by the desired temperature of the fluid

transported can be considered.

  In the example illustrated, and to avoid any over-

  heats in a start-up phase of the heating device, the regulator 10 is also controlled by a

  probe 12 measuring the temperature of the wall of the pipe 1.

  The supply could of course be single-phase.

  The voltage is generally kept below 100

  volts The hose is preferably made of stainless steel

  dable With a pipe with an internal diameter of 18 mm and external 20 mm and a power supply of 32 KW or 513 amps on 36.4 volts, we obtain for a distance of -6-

  6 mm between two supply flanges a specific power of 12.1 W / cm 2.

  It is possible to determine the optimal shape of the section of the pipe 1 in order to obtain a uniform heating of the conveying fluid; this section can be ovoid, oval or

rectangular for example.

  The surface of the pipe 1 in contact with the fluid to

  heating may include fixings, fins, spi-

  rales, etc to favor the conduction of heat and the turbulence of the flow always in order to improve the conduction and thus to achieve a heating also

homogeneous as possible of the fluid.

  To be able to use high amperages, the supply flanges 4 can be provided with distribution plates.

  bution to increase their surface in contact with

hose 1.

  When the pipe 1 has several straight parts (la) each of these is provided with a pair of

  supply flanges 4 connected in series or in parallel20 to an electrical supply 7.

  We can finally plan to have the pipe 1 in an outer insulating tube which allows the circulation of the

  fluid to be heated on both sides of the wall of the pipe 1 and thus reduce losses of dissipated heat.

-7-

Claims (7)

  1 device for heating a fluid comprising a pipe in which this fluid circulates, this pipe comprising at least one rectilinear portion (la) electrically conducting crossed by an electric current causing its heating by Joule effect and consequently the heating of the fluid, characterized in that it comprises supply flanges (4) which are fixed in an adjustable manner along this rectilinear portion (la) so as to be able to vary, for a given supply power, the specific power dissipated by the pipe depending on   the distance separating these supply flanges (4).   2 Device according to claim 1, characterized in that each supply flange (4) comprises two halves (4 a, 4 b) enclosing the pipe and fixed one to   the other and against the pipe by clamping means (5).   3 Device according to claim 1 or claim-   tion 2, characterized in that each supply flange   tation (4) includes a distribution plate increasing   its contact surface with the surface of the pipe.   4 Device according to one of the preceding claims,   characterized in that the adjacent flanges (4) of two adjacent pairs, located on either side of an 8 - bend (2) of the pipe, are electrically connected to each other.   Device according to one of the preceding claims,   characterized by the fact that it comprises three straight portions (la) of pipe, each provided with a pair of supply flanges (4) connected to one of the phases   a three-phase power supply (7,8,9).   6 Device according to one of claims 1 to 4, ca-   characterized by the fact that it comprises at least two straight parts (la) of pipe, each being provided with a pair of supply flanges (4) connected in series or in   parallel on a power supply (7).   7 Device according to one of claims 5 or 6, ca-   characterized by the fact that the power supply (7) is a low voltage power supply (less than 100 volts). 8 Device according to claim 7, characterized in that it comprises an all-or-nothing regulation of the supply of the flanges (4) controlled by a regulator (10) controlled by a probe (11) detecting the temperature of the fluid.   9 Device according to claim 8, characterized by   the fact that it includes a second temperature probe (12)   ture detecting the temperature of the pipe and also controlling the regulator (10). 9 -   Device according to one of the preceding claims,   characterized in that it comprises a sealed enclosure around the pipe also serving for the transport of the fluid.