Electric heating – Inductive heating – With heat exchange
Reexamination Certificate
2001-02-14
2002-10-15
Leung, Philip H. (Department: 3742)
Electric heating
Inductive heating
With heat exchange
C219S629000, C219S667000
Reexamination Certificate
active
06465765
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fluid heating apparatus, more particularly an electromagnetic induction heating type fluid heating apparatus, for heating various types of fluid, such as gas and liquid, to be supplied through piping to a substrate processing section in a substrate processing apparatus which performs required processes upon substrates including semiconductor substrates and substrates for flat panel display.
2. Description of the Background Art
For a substrate processing apparatus, e.g. a reduced-pressure drying apparatus for substrates, it is necessary to heat alcohol vapor, e.g. isopropyl alcohol (IPA) vapor, up to a predetermined temperature to supply the vapor through piping into a chamber in which a substrate is contained under an atmospheric pressure. To heat the IPA vapor, an apparatus has been generally used which comprises a resistance heater on an outer peripheral surface of the piping made of stainless steel or the like and which heats the piping by heat transfer from the resistance heater to indirectly heat the IPA vapor flowing through the piping. Recently, an attempt has been made to heat the fluid flowing through the piping by the use of electromagnetic induction.
FIG. 2
is a schematic vertical sectional view of an apparatus for heating fluid by the use of electromagnetic induction. The fluid heating apparatus of
FIG. 2
comprises: a heater case
40
interposed in piping (not shown) through which fluid to be heated is passed; a coil
42
wound about part of an outer peripheral surface of the heater case
40
; a power supply unit (not shown) for feeding a high-frequency current through the coil
42
; and a heating element
44
disposed inside the heater case
40
.
The heater case
40
comprises: a cylindrical part
46
made of a non-magnetic material such as fluororesin; an entrance closing plate
48
having a fluid inlet
50
connected in communication to the piping through which the fluid is passed and a packing
52
for closing a first opening surface of the cylindrical part
46
; and an exit closing plate
54
having a fluid outlet
56
connected in communication to the piping through which the heated fluid is fed out and a packing
60
for closing a second opening surface of the cylindrical part
46
. Thus, the heater case
40
has an enclosed structure.
The heating element
44
, the structure of which is not specifically illustrated, typically comprises a plurality of regularly arranged thin plates, e.g. corrugated plates, made of an electrically conductive material such as ferritic stainless steel so that the fluid flows through the spaces between the thin plates. A temperature sensor
62
includes a temperature sensing element, e.g. a thermocouple
64
, inserted in the heater case
40
and disposed downstream from and adjacent to the heating element
44
. The temperature sensor
62
measures the temperature of the heating element
44
. The heater case
40
is also provided with a temperature sensor
66
for measuring the temperature of the fluid flowing out of the heater case
40
. The temperature sensor
66
includes a temperature sensing element, e.g. a thermocouple
68
, inserted in the heater case
40
and disposed near the outlet thereof. The temperature sensors
62
and
66
output respective temperature detection signals to a controller not shown. The controller is connected to the power supply unit and an alarm (both not shown).
In the fluid heating apparatus shown in
FIG. 2
, when the power supply unit feeds the high-frequency current through the coil
42
, a magnetic flux is developed to induce eddy currents in the respective thin plates of the heating element
44
in the heater case
40
, thereby evolving Joule heat in the thin plates because of the specific resistance of the material of the thin plates, which results in heat generation from the heating element
44
. The cylindrical part
46
of the heater case
40
, which is made of a non-magnetic material, does not generate heat in itself. The heat generated by the heating element
44
is transferred and applied to the fluid flowed from the piping through the fluid inlet
50
into the heater case
40
during the passage of the fluid through the position of the heating element
44
. The fluid heated to a raised temperature flows out of the heater case
40
through the fluid outlet
56
into the piping. In this process, the controller outputs a control signal to the power supply unit, based on the fluid temperature detection signal detected by the temperature sensor
66
, to control the temperature of the fluid flowing out of the heater case
40
to reach a target temperature. The controller also compares the temperature near the heating element
44
which is detected by the temperature sensor
62
with a preset warning temperature. When the temperature detected by the temperature sensor
62
exceeds the warning temperature, the controller outputs a signal to the alarm to activate the alarm, and outputs a signal to the power supply unit to control the power supply unit to shut off the supply of electric power from the power supply unit to the coil
42
or weaken the output to the coil
42
.
Unfortunately, the conventional fluid heating apparatus as shown in
FIG. 2
presents problems to be described below and therefore is not used as a fluid heater for the apparatuses for processing the semiconductor substrates and the flat panel substrates. The conventional fluid heating apparatus comprises the heating element
44
including the plurality of regularly arranged thin plates, e.g. corrugated plates, for the purpose of increasing the heat transfer area of the heating element
44
. This results in a complicated structure of the heating element
44
and large amounts of dead space, making it difficult to carry out sufficient initial cleaning of the heating element
44
. Further, the thin plates of the heating element
44
are thermally expanded into sliding contact with each other during the heat generation from the heating element
44
or are vibrated under the influence of flow of the fluid, particularly gas, passing through the position of the heating element
44
. As a result, a large number of particles are produced by the heating element
44
.
Additionally, the heating element
44
must be incorporated into the heater case
40
which is enclosed, with the fluid inlet
50
and the fluid outlet
56
connected in communication to the piping, and which has the coil-wound part made of a non-magnetic material. Thus, the heater case
40
has a complicated structure including flanged parts and the like, which leads to a large number of locations in which contaminants such as particles are deposited. As a result, once the inside of the heater case
40
is contaminated by the particles or the like, it is impossible to easily remove the particles. Therefore, the conventional fluid heating apparatus is disadvantageous in being incapable of suppressing the generation of the particles.
Furthermore, the conventional fluid heating apparatus has a complicated structure such that the heating element
44
including the plurality of thin plates, e.g. corrugated plates, is incorporated in the heater case
40
. Such a complicated structure causes the flow of fluid passing through the heater case
40
to stay at some locations to prevent the uniform heat exchange of the entire heating element
44
with the fluid. As a result, the heating element
44
is partly overheated to melt, thereby suffering damages, or is reduced in heat exchange efficiency. Thus, the conventional fluid heating apparatus is not capable of heating the fluid as desired to have the heat transfer area greater than necessary, resulting in increased costs.
Even if an attempt is made to monitor the temperature of the heating element
44
which reaches the highest temperature in order to ensure an explosion-proof property, it is structurally difficult for the conventional fluid heating apparatus to place the thermocouple
64
of the temperature sensor
62
in contact with the
Katayama Masakazu
Kojimaru Tomonori
Muraoka Yusuke
Oku Seiji
Leung Philip H.
Omron Corporation
Ostrolenk Faber Gerb & Soffen, LLP
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