WO2021059288A2

WO2021059288A2 - Blow heater for heating and disinfection of viruses and bacteria in gaseous medium

Info

Publication number: WO2021059288A2
Application number: PCT/IL2021/050117
Authority: WO
Inventors: Ilan Riess; Liran RIESS
Original assignee: Ilan Riess; Riess Liran
Priority date: 2020-09-30
Filing date: 2021-02-02
Publication date: 2021-04-01
Also published as: WO2021059288A3

Abstract

A blow heater for heating and disinfecting a gaseous medium containing viruses and bacteria comprises: a main conduit; an internal conduit nested within the main conduit; and an impeller configured for blowing the gaseous medium via the main conduit. A first part of the flow conducted by the internal conduit is heated by the heater. A second part of the flow within a space between the walls of the internal conduit and the main conduit is conducted without heating. The blow heater comprises a turbulence chamber disposed downstream to the main conduit. The turbulence chamber comprises a housing connected to the main conduit and a 3d turbulating structure accommodated within the housing. The 3d turbulating structure is configured for blending the first and second parts of the flow of the gaseous medium and homogenizing the temperature of the gaseous medium.

Description

BLOW HEATER FOR HEATING AND DISINFECTION OF VIRUSES AND BACTERIA IN GASEOUS MEDIUM

FIELD OF THE INVENTION

The present invention relates to blow (fan) heaters and, more particularly, to blow heaters configured for heating and disinfecting a gaseous medium containing viruses and bacteria therewithin.

BACKGROUND OF THE INVENTION

In 2020, Covid-19 pandemic has drawn the world attention to the need to disinfect room air from viruses and bacteria. This is of special need when the virus or bacteria leads to a high fatal rate, a situation that arises from time to time. Disinfection is also of need for less aggressive viruses or bacteria as those may lead to large scale illness and the associated economic burden as well as to a certain fatal rate. It is therefore desirable to be able to disinfect room air. This is in particular important in cold regions and in the winter in most places around the globe, as rooms are closed and a virus or bacteria from an infected person there, may accumulate. Thus, the need of disinfection of room air in closed rooms of schools, hospitals, clinics, offices, shops and even in many private houses, becomes apparent. There are a few methods suggested for disinfection of air, however there is only one that is certain for disinfecting all viruses and bacteria and it is by heating. Any virus or bacteria cannot withstand a temperature high enough for a given length of time. Air disinfection can, thus, be achieved by re-circulating air into a heater of a sufficiently high temperature and for a corresponding sufficiently long exposure time. The exposure time is determined by the residence time in the hot zone. The exposure time can be reduced to a fraction of a second provided the temperature is sufficiently high. Thus, a blow heater that can heat air to a sufficiently high temperature, for a sufficiently long residence time will serve for both heating and effective disinfection of even difficult to disinfect viruses and bacteria which require elevated temperature for disinfection.

In contrast to heating, filters are used by others for disinfection air¹. However, the best commercial filters have pores of 0.3 qm (https://www.grainger.com/know- how/equipment-infomration/kh-what-is-merv-rating-air-filter- rating-chart) while Covid-19 virus has a size of 0.1 mm (https://www.news-medical.net/health/The-Size- of-SARS-CoV-2-Compared-to-Other-Things.aspx) Further, the virus will accumulate on the filter surface for hours or days, depending on material, temperature and humidity Those filters demand higher pressure air supply. They also require replacement every three months. An alternative method also used, is disinfection by ultra violet light in the C band, UVC. If the virus is shielded from the radiation, e.g. sitting on a dust particle and shielded, it is not destroyed. The required exposure time seems to be long, minutes, the effectiveness of UVC lamps in inactivating Covid-19 is not yet known (https ://www.fda. gov/medical -devices/coronavirus-covid- 19 -and - medical-devices/uv-lights-and-lamps-ultraviolet-c-radiation-disinfection-and- coronavirus). Further, UVC radiation should not reach the eyes and skin of persons. An additional disinfection method examined is ionization of air. However, there are only preliminary results mentioning, in a wage form, 10 min exposure of the air for 99% disinfection of a simulant (https://www.prnewswire.com/news-releases/plasma- air-ionization-proven-to-reduce-coronavirus-surrogate-ms2-bacteriophage-by-99-in- independent-spanish-testing-301076955.html ) . The effectiveness in high-rate disinfection, with exposure time less than one second is then questionable.

To operate as a ventilation device, of acceptable small size, that circulate a large amount of air, the air velocity in the device has to be high, hence the exposure time to high temperature has to be short, a fraction of a second. For example, Covid-19 virus is claimed, by some, to be destroyed when exposed to 70 °C for 30 min. while others claim it is destroyed when exposed to 54 °C for 30 min. Model calculation, by us, starting with the more conservative result of 70 °C and 30 min. yields that an exposure time of 0.1 s requires heating the air to 200 °C.

This high temperature or even higher ones, raise safety issues as the hot air and hot device may cause bums and may ignite, melt and distort surrounding objects. The patent here provides the answer to this safety problem and the details of the heating chamber designed to assure a sufficiently long residence time of air in the hot zone.

The technology requirements for constructing the novel ventilation device are for a small scale (room) application those of a blow heater, and for a large scale (whole house of large building) application those of a ventilation system, though the design is quite different from conventional systems. As the safety issues and residence time requirements of the large ventilation systems are similar to those of the smaller blow heater and the solution presented here is similar as well, we discuss here the solution by example of novel design of blow heaters that allow disinfection of air from all kinds of viruses and bacteria. This solution presented for blow heaters enables any persons skilled in the arts to apply the solution also to large scale ventilation systems.

A blow (fan) heater is a heater which includes an impeller forcing air to pass via a heat source (e.g. a heating element). The air passed through the heating element becomes hot then transfers the heat acquired from the heater to the surrounding.

US 5841943 discloses an axial flow hair dryer comprises a main housing and an outer duct secured to the main housing with the axis of the outer duct coincident with the axis of the main housing and with the axial air outlet of the main housing disposed within the outer duct to form an annular air intake between the main housing and the outer duct. A first fan stage and first stator stage are disposed within the main housing and a second fan stage and second stator stage are disposed within the outer duct. A handle depending from the main housing holds a motor that is mounted using vibration- absorbing material to inhibit the propagation of noise generated by the motor. A flexible shaft connects the motor to a drive shaft that carries both fan stages. Resistance heating wires are wrapped around the vanes of the first stator stage to heat the air flowing through the hair dryer.

SUMMARY OF THE INVENTION

It is hence one object of the invention to disclose blow heater for heating and disinfecting a gaseous medium containing viruses and bacteria therewithin. The aforesaid blow heater comprises: (a) a main conduit having an input terminal and an output terminal; said main conduit having a first aperture defined by a wall thereof; (b) an impeller configured for blowing said gaseous medium via said main conduit from said input terminal to said output terminal; (c) an internal conduit having an input terminal and an output terminal; said secondary conduit having a second aperture defined by a wall thereof; (d) a heater mounted in said internal conduit by mounting means; said heater being configured for heating and disinfecting a first part of said gaseous medium. The second aperture is smaller than said first aperture such that said internal conduit is nested within said main conduit thereby a second part of said flow within a space between said walls of said internal conduit and said main conduit is conducted without contacting the heater while the first part of said flow conducted by said internal conduit is contacting said heater.

It is a core purpose of the invention to provide the blow heater further comprising a temperature homogenizing chamber disposed downstream to said output terminal of said main conduit; said temperature homogenizing chamber is configured for turbulating and blending the first and second parts of the gaseous medium flow. The temperature homogenizing chamber comprises a housing connected to said output terminal of said main conduit and an output aperture for discharging a heated, homogenized and disinfected gaseous medium into surrounding media.

Another object of the invention is to disclose a blow heater for heating and disinfecting a gaseous medium containing viruses and bacteria therewithin. The aforesaid blow heater comprises: (a) a main conduit having an input terminal and an output terminal; said main conduit having a first aperture defined by a main wall of said main conduit; (b) a first impeller configured for blowing said gaseous medium via said main conduit from said input terminal to said output terminal; (c) an internal conduit having an input terminal and an output terminal; said secondary conduit having a second aperture defined by an internal wall of said internal conduit; (d) a heater mounted in said internal conduit by mounting means; said heater being configured for heating and disinfecting a first part said gaseous medium.

The second aperture is smaller than said first aperture such that said internal conduit is nested within said main conduit thereby a second part of said flow within a space between said walls of said internal conduit and said main conduit is conducted without contacting the heater while the first part of said flow conducted by said internal conduit is contacting said heater.

It is another core purpose of the invention to provide the blow heater comprising a freely rotatable propeller disposed in said main conduit downstream to said internal conduit and configured for blending said first and second parts and, respectively, of said flow of said gaseous medium; said main conduit comprises a throat portion located downstream to said propeller; said throat portion has at least one side aperture in said main wall such that a surrounding gaseous medium is admixed by Venturi pumping to said blended and disinfected gaseous medium.

The blow heater further comprises a temperature homogenizing chamber disposed downstream to the output terminal of the main conduit. The temperature homogenizing chamber is configured for turbulating and blending the first and second parts of the flow with admixed surrounding gaseous medium. The temperature homogenizing chamber comprises a housing connected to the output terminal of the main conduit and an output aperture for discharging a heated, homogenized and disinfected gaseous medium into surrounding media.

A further object of the invention is to disclose a blow heater for heating and disinfecting a gaseous medium containing viruses and bacteria therewithin. The aforesaid blow heater comprises: (a) a main conduit having an input terminal and an output terminal; said main conduit having a first aperture defined by a main wall of said main conduit;

(b) an internal conduit having an input terminal and an output terminal; said secondary conduit having a second aperture defined by an internal wall of said internal conduit;

(c) a first impeller configured for blowing said gaseous medium via said internal conduit; (d) a heater mounted in said internal conduit by mounting means; said heater being configured for heating and disinfecting a first part of said gaseous medium.

The second aperture is smaller than said first aperture such that said internal conduit is mounted within said main conduit.

It is another core purpose of the invention to provide the internal conduit comprises a throat portion located downstream to said heater in said internal conduit. The throat portion has at least one side aperture such that a surrounding gaseous medium from said main conduit is drawn along the internal conduit starting from the cold zone of the internal conduit into the side aperture of said internal conduit and said gaseous medium from said main conduit is admixed to heated and disinfected gaseous medium within said internal conduit. The throat portion is connected to a temperature homogenizing chamber disposed downstream to said throat portion such that heated and disinfected gaseous medium mixed with said surrounding gaseous medium flows thereto; said temperature homogenizing chamber comprises a housing connected to said output terminal of said main conduit and an output aperture for discharging a heated, homogenized and disinfected gaseous medium into surrounding media. The temperature homogenizing empty chamber is configured for turbulating and blending the heated and disinfected gaseous medium mixed with said surrounding gaseous medium for discharging a heated, homogenized and disinfected gaseous medium into surrounding media.

A further object of the invention is to disclose a blow heater for heating and disinfecting a gaseous medium containing viruses and bacteria therewithin. The aforesaid blow heater comprises (a) a main conduit having an input terminal and an output terminal; said main conduit having a first aperture defined by a main wall of said main conduit; (b) an internal conduit having an input terminal and an output terminal; said secondary conduit having a second aperture defined by an internal wall of said internal conduit; (c) a heater mounted in said internal conduit; said heater being configured for heating and disinfecting a first part of said gaseous medium; (d) a first impeller configured for blowing a first part of said gaseous medium via said internal conduit.

The second aperture is smaller than said first aperture such that said internal conduit is mounted within said main conduit thereby a second part of said of said gaseous medium flows within a space between said walls of said internal conduit and said main conduit is conducted without contacting the heater while the second part of said flow conducted by said internal conduit is contacting said heater. A second impeller configured for blowing the second part of said gaseous medium via said space. The second impeller is positioned near the cold zone on the internal conduit.

The blow heater further comprises a temperature homogenizing chamber disposed downstream to said output terminal of said main conduit. The temperature homogenizing chamber is configured for turbulating and blending the first and second parts of the flow. The temperature homogenizing chamber comprises a housing connected to said output terminal of said main conduit and an output aperture for discharging a heated, homogenized and disinfected gaseous medium into surrounding media.

A further object of the invention is to disclose the temperature homogenizing chamber comprising a 3d turbulating structure accommodated therewithin said temperature homogenizing chamber, configured for blending said first and second parts of said flow of said gaseous medium and homogenizing its temperature before discharging said heated and disinfected gaseous medium from said output aperture.

A further object of the invention is to disclose the 3d turbulating structure comprising at least one element selected from the group consisting of a plate-like turbulating element angularly disposed relative to a homogenized flow, an aperture disposed along a flow of said heated and disinfected gaseous medium, an open pore lattice-like structure, a freely rotatable rotator and any combination thereof.

A further object of the invention is to disclose said 3d turbulating structure which is made of a refractory material.

A further object of the invention is to disclose the mounting means comprising at least one tie-rod securing said internal conduit to said main conduit.

A further object of the invention is to disclose blow heater comprising at least one temperature sensor, at least one flow meter and a controller configured for monitoring temperature of a heated flow and flow rate and controlling operation parameters of said heater and impeller.

A further object of the invention is to disclose the heater compartment being part of the internal conduit, comprising at least one heating element and the logic for controlling the temperature there.

A further object of the invention is to disclose the controller configured for energizing the heating elements such that power radiated by the heating elements heat the gaseous medium up to temperature thereof detected by the temperature sensor which is effective for disinfecting the gaseous medium at calibrated flow rate or at detected flow rate by the flow rate sensor.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the invention and to see how it may be implemented in practice, a plurality of embodiments is adapted to now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which

Fig. 1 is a schematic longitudinal cross-sectional view of an exemplary embodiment of a blow heater; Fig. 2 is a schematic transverse cross-sectional view of an exemplary embodiment of a blow heater;

Figs 3 to 5 are schematic longitudinal cross-sectional diagram of alternative embodiments of a blow heater;

Fig. 6 is a graph of dependence of residence time required for destroying viruses and bacteria contained in an air flow on temperature of the air flow; and

Figs 7 to 9 are schematic longitudinal cross-sectional diagram of alternative heater arrangements provided with temperature sensors and flow meters.

DETAILED DESCRIPTION OF THE INVENTION

The following description is provided, so as to enable any person skilled in the art to make use of the invention and set forth the best modes contemplated by the inventor of carrying out this invention. Various modifications, however, are adapted to remain apparent to those skilled in the art, since the generic principles of the present invention have been defined specifically to provide a blow heater for heating and disinfecting a gaseous medium containing viruses and bacteria therewithin and keeping the temperature of the exhaust gas moderate to avoid bums as well as ignition, melting and distortion of surrounding objects.

The present invention provides a blow heater concurrently functioning as heating means and a disinfector by heating a gaseous medium carrying viruses and bacteria within surrounding environment. Specifically, airborne virus COVID-19 is destroyable at elevated temperatures. Capacity of the proposed device can be improved by increase in temperature of the heating and of heating power because a flow rate of the gaseous medium can be increased either. For practical reasons a temperature of 150-300°C would be preferred. To avoid possible burns of incautious users and accidental ignition, melting and distortion of materials in surrounding environment, the heated gaseous flow is blended with the unheated one such that the temperature of the mixed flow is lower than that of the heated gaseous flow and safe in terms of possible burns and accidental ignition and damage to the surrounding.

Reference now made to Fig. 1, presenting blow heater 100 for heating and disinfecting a gaseous medium 10 containing viruses and bacteria therewithin. Main conduit 20 has input terminal 21 and output terminal 23. Gaseous flow 10 from surrounding environment is pushed into input terminal 21 by impeller 30 of main conduit 20. Numeral 50 refers to an internal conduit nested into main conduit 20. Wall 27 defines aperture 25 of main conduit 20 conducting a gaseous flow blown by impeller 30. Wall 53 of internal conduit 50 defines its internal aperture 55. Heater 60 is disposed within internal conduit 50. Central part 43 of the gaseous flow blown by impeller 30 goes via heater 60. A heated gaseous flow is indicated as 47. According to one embodiment of the present invention, blow heater 100 comprises at least one of temperature sensors 61 and 62, at least one flow meter 33 and a controller (not shown) configured for monitoring the temperature of heated flow 47 and the total flow rate 43 and 41 and controlling operation parameters of heater 60 and impeller 30. Other locations of the abovementioned temperature sensors and flow meters are in the scope of the present invention. Peripheral gaseous part 41 goes within a space between walls 27 and 53 and does not come in contact with heater 60. Temperature homogenizing chamber 70 is connected to output terminal 27 of main conduit 20 and comprises 3d turbulating structure 75 accommodated in housing 72 and an output aperture 90 for discharging a heated, homogenized and disinfected gaseous medium into surrounding media. 3d turbulating structure 75 is configured for blending central and peripheral gaseous flow parts 47 and 41, and homogenizing the mixed gaseous medium temperature before discharging heated and disinfected gaseous medium 80 from output aperture 90. According to one embodiment of the present invention, the temperature homogenizing chamber 70 comprising a 3d open pore grid of refractory material such as stainless steel or ceramics. Impeller 30 is secured to conduit 20 by one or more tie-rods 32.

Reference is now made to Fig. 2 presenting a transverse cross-sectional view through heater 60, the view being an exemplary embodiment of the blow heater. As mentioned above, internal conduit 50 is nested within main conduit 20. Electric heater 60 is mounted in internal conduit 50 and is configured for heating the gas flow going through internal conduit 50. As shown in Fig. 2, internal conduit 50 is secured to main conduit 20 by means of a number of tie-rods 51.

Reference is now made to Fig. 3 presenting first alternative embodiment 100a of the blow heater. Embodiment 100a is provided with propeller 87 mounted in chamber 83 and freely rotatable therewithin such that the gaseous flow is turbulated by propeller 87 and thus is blended. Propeller 87 is secured to the main conduit 20 by one or more tie-rods 88. In addition, main conduit 20 has throat portion 81 located downstream to internal conduit 50 and propeller 87. Throat portion 81 has at least one side aperture 85. Surrounding gas is drawn into main conduit 20 by Venturi pumping. Temperature homogenizing chamber 70 is connected downstream to throat portion 81. The temperature homogenizing chamber 70 has a smaller entrance aperture, as compared to the cross-sectional area of other parts of the temperature homogenizing chamber, resulting in a turbulating flow of the gaseous medium in it and blending of the different contributions of the gaseous medium.

Reference is now made to Fig. 4 presenting a second alternative embodiment 100b of the blow heater. Impeller 30 blows gaseous medium 10 into internal conduit 50 through heater 60. Downstream to heater 60, internal conduit 50 is provided with throat portion 81 having at least one side aperture 85. In this embodiment, flow 43 is pushed through heater 60. Then, heated flow 47 passes through throat portion 81 and entrains unheated flow 41 thereinto by Venturi pumping. When reached temperature homogenizing chamber 70, heated and unheated flows are intermixed by turbulating flow. Unheated flow 41 enters the space between conduit 50 and conduit 20 upstream from the region of heater 60 and flows along the outer surface of conduit 50 towards opening 85.

Reference is now made to Fig. 5 presenting a third alternative embodiment 100c of the blow heater. Embodiment 100c is provided with additional impeller 31. While impeller 30 forces surrounding gas 10 into internal conduit 50 through heater 60, impeller 31 blows surrounding gas 11. Impeller 31 is located upstream of the region of heater 60 and unheated flow 41 is flowing along the outer surface of conduit 50 towards homogenizing chamber 70. According to one embodiment of the present invention, blow heater 100c comprises at least one of temperature sensors 61 and 62, and at least one flow meter 33 and 34 and a controller (not shown) configured for monitoring the temperature of heated flow 47 and the flow rates 43 and 41 and controlling operation parameters of heater 60 and impellers 30 and 31. Flow 43 passes through heater 60. After heater 60, heated gaseous flow 47 and gaseous flow 41 reach temperature homogenizing chamber 70. According to one embodiment of the present invention, the 3d turbulating structure inside the temperature homogenizing chamber 70 comprises a number of plate-like members 78 mounted angularly relative to a homogeneous gaseous flow direction. Impeller 31 is secured to main conduit 20 by one or more tie-rods 33.

It is known in the art that the heater is used for raising the temperature of a gas flow, such as air flow, so that the gas temperature is higher than a required temperature over an extended range inside the space of the heater. The application of such a heater can be for the disinfection of a gas from viruses and bacteria. The disinfection of a gas by heating requires that the virus or bacteria is exposed to a given temperature for a length of time. This required exposure time is determined by the residence time, t_res, in the hot zone. It decreases with the increase in temperature.

Reference is now made to Fig. 6, presenting a graph of computer-simulated dependence of residence time required for destroying viruses and bacteria contained in an air flow on temperature of the air flow. Assuming that disinfection of Covid-19 virus taking residence time of 30 min (1800 s) requires heating the air flow up to 70 °C. The reaction rate is thermally activated, being governed by an activation energy of 1 eV. In this model calculation, the required residence time for disinfection is shortened from 1800 s at 70 °C to 0.165 s at 200 °C and to even shorter time at higher temperatures.

Reference is now made to Figs. 7 to 9 presenting exemplary embodiments directed for feedbacking between airflow rate and its temperature in order to provide effective disinfection of the viruses and bacteria contained in it.

Referring to Fig. 7, internal conduit 50 is preferably made of a refractory metal such as stainless steel or made of ceramics such as alumina or magnesia. Thermal insulator 77 on conduit 50 is optional. Thermal insulator 77 reduces heat losses and allows for a more uniform temperature profile. However, a flow of gas around the conduit can also be used as a thermal insulator and the heat absorbed by the outer gas flow used for heating the latter. Flow meter 33 for determining the air flow velocity is optionally placed on the inlet side of the gas stream. Without flow meter 33, the flow velocity is regulated by calibrating the power applied to the impeller (not shown) that drives incoming gas flow 43. Single temperature sensor 62 is configured for monitoring the temperature of gas downstream 47 from heating element 60. Sensor 62 is placed at a distance L from heating element 60. Distance L is preferably between 1 to 100 cm for small and medium, size heaters. According to one embodiment, heating element 60 is a flat heating element made from open coils connected to form a flat arrangement. Tubular or finned heating elements are also in the scope of the present invention.

The control algorithm applicable to the embodiment on Fig. 7 is the following: a. It is based on the approximation that the hottest region is at the heating element (ignoring nonuniformity in the temperature along the plane of the heating element) and that the temperature decreases gradually as the gas proceeds towards the temperature senor (due to heat losses). Thus, the temperature measured by the temperature sensor is a lower limit for the gas temperature in the region of distance L, between the heating element and the position of the temperature sensor. The temperature measured by the sensor is used as the control parameter for the electrical power feeding the heating element. b. The flow rate V m³/s of the gas, say air, is a parameter that is dictated by the user. For example, 3 m³/min = 0.05 m³/s. The velocity of the gas is then determined by the cross-section S of the conduit, for example 0.04 m². The gas velocity v is v= V/S which is 0.05/0.04 = 1.25 m/s. c. The residence time, t_res, at a given gas flow rate is t_res=L/v. For a distance L= 0.125 m the numerical example yields t_res=0.125/1.25=0.1 s. d. To allow disinfection during a residence time t_res the controller (not shown in the figures) has to supply power to the heating element so that the temperature of the sensor is T(t_res) the temperature required to disinfect the gas within the time t_res. (The control allows the temperature on the sensor to deviate by a small predetermined value up to +DT from the target temperature T(t_res), DT being preferably between 1 to 5 °C). For example, looking at Fig. 6 the temperature for t_res=0.1 s should be regulated to 205 °C. Considering air flow of 3 m³/min, under 1 bar pressure, being heated from 20 °C to 205 °C, the power required for heating the gas, being air, is: 11.1 kW. e. If the distance L is 0.5 m rather than 0.125 m the example yields: t_res=0.5/l.25=0.4 s. From Fig. 6, the necessary temperature for disinfection drops to: T(t_res)= 184 °C (and the power required for heating 3 m³/min air from 20 °C to 184 °C drops to: 9.8 kW). f. The power given in the previous examples uses the control temperature as the actual temperature of the gas. However, with a single heating element the gas temperature may be quite far from being uniform over an extended distance L due to heat losses to the surrounding. In this case the gas temperature is in most of the distance L higher than the control

thus, demanding additional power over that required if the temperature profile would be more uniform, close to

Reference is now made to Figs. 8 and 9, presenting another embodiment of temperature sensor-flowrate senor arrangement. The temperature profile can be shaped by adding heating elements in the heating chamber. The advantage is that one can better control the temperature profile of the gas without the need to use a “minimum” temperature as a gross approximation for the actual temperature along the distance L in the heating chamber. A plurality of heating elements can be used as well as a plurality of temperature sensors for better determining the temperature profile prevailing in the heating chamber under gas flow.

We now discuss a heating chamber with three heating elements, shown in Fig. 8. Heating element 60a placed upstream is a pre-heater and two other heating elements 60b and 60c allow to form a more uniform temperature profile.

The algorithm for controlling the temperature of the heater is similar to the disclosed above. Single temperature control sensor 62 provides information that is used to control the power in all three heating elements. This is possible after calibrating the partition of the power required in each heating element under different gas flow rates. Referring to Fig. 9, a plurality of temperature sensors is provided and eliminates the need for a-priori calibration of the partitions of power supplied to the different heating elements for each gas flow rate. Fig. 9 exhibits a heating chamber with three heating elements as in the previous example, however with three temperature sensors 62a, 62b and 62c. Temperature sensor 62a is placed downstream, close to heating element 60b. Temperature sensor 62b is placed midway between heating element 60b and heating element 60c. Temperature senor 62c is placed downstream close to heating element 60c. In this embodiment, the power for heating elements 60a and 60b is controlled separately from the power for heating element 60c.

The control algorithm in Fig. 9, is different from the algorithms relating to Figs 7 and 8. Temperature sensors 62a to 62c allow providing a sufficiently uniform temperature profile of the output airflow. The required temperature,

is calculated for the given residence time being fixed by the gas flow velocity. At the first step, temperature T₁ measured by temperature sensor 62a is used to control the power supplied to heating elements 60a and 60b with a prefixed partition in the power supplied to each of two heating elements 60a and 60b. The target is to change T₁ until

within

At the second step, temperature

measured by sensor 62c is used to control the power supplied to heating elements 62c until

within At the third step, temperature T2 is compared with

If temperature T2 is lower than

the controller energizes heating elements 60a and 60b such that temperature T2 of the airflow is used as control signal, instead of T₁ as in the first step. In this case, the power is provided to heating elements 60a and 60b such that T2 becomes

Then, the cycle starts all over again going through steps 1, 2 and 3. Alternatively, only steps 2 and 3 are repeated or, in a further alternative option, only step 3 is repeated continuously for the purpose of controlling the heating.

For a short residence time of the order of 0.1 s or shorter, the response time of the whole heat control procedure will depend on the response time of the heating elements which is expected to be longer than 0.1 s. The time of each heating control cycle is expected to be of the order of a few minutes at most. The control procedure is, preferably, continuously active to cope with gas temperature changes, gas humidity changes, heating chamber material temperature change, etc.

Claims

Claims:

1. A blow heater for heating and disinfecting a gaseous medium containing viruses and bacteria therewithin; said blow heater comprising: a. a main conduit having an input terminal and an output terminal; said main conduit having a first aperture defined by a wall thereof; b. a first impeller configured for blowing said gaseous medium via said main conduit from said input terminal to said output terminal; c. an internal conduit having a second aperture defined by a wall thereof; d. a heater mounted in said internal conduit by mounting means; said heater being configured for heating to a controlled temperature and disinfecting a first part of said gaseous medium; said second aperture is smaller than said first aperture and a length of said internal conduit is shorter than a length of said main conduit such that said internal conduit is nested within said main conduit thereby a second part of said flow of gaseous medium within a space between said walls of said internal conduit and said main conduit is conducted without contacting the heater while the first part of said flow of gaseous medium conducted by said internal conduit is contacting said heater; said internal conduit is mounted to said main conduit by mounting means; wherein said blow heater further comprises a temperature homogenizing chamber disposed downstream to said output terminal of said main conduit; said temperature homogenizing chamber is configured for turbulating and blending said first and second parts of said flow with each other; said temperature homogenizing chamber comprises a housing connected to said output terminal of said main conduit and an output aperture for discharging a heated, homogenized and disinfected gaseous medium into surrounding media.

2. A blow heater for heating and disinfecting a gaseous medium containing viruses and bacteria therewithin; said blow heater comprising: a. a main conduit having an input terminal and an output terminal; said main conduit having a first aperture defined by a main wall of said main conduit; b. a first impeller configured for blowing said gaseous medium via said main conduit from said input terminal to said output terminal; c. an internal conduit having a second aperture defined by an internal wall of said internal conduit; d. a heater mounted in said internal conduit by mounting means; said heater being configured for heating to a controlled temperature and disinfecting a first part of said gaseous medium; said second aperture is smaller than said first aperture and a length of said internal conduit is shorter than a length of said main conduit such that said internal conduit is nested within said main conduit thereby a second part of said flow of gaseous medium within a space between said walls of said internal conduit and said main conduit is conducted without contacting the heater while the first part of said flow of gaseous medium conducted by said internal conduit is contacting said heater; said internal conduit is mounted to said main conduit by mounting means; wherein said blow heater comprises a freely rotatable propeller disposed in said main conduit downstream to said internal conduit and configured for blending said first and second parts of said flow of said gaseous medium; said main conduit comprises a throat portion located downstream to said internal conduit and freely rotatable propeller; said throat portion has at least one side aperture in said main wall such that a surrounding gaseous medium is admixed by Venturi pumping to said heated and disinfected gaseous medium; wherein said blow heater further comprises a temperature homogenizing chamber disposed downstream to said throat portion forming a small entrance aperture to the temperature homogenizing chamber as compared to the cross sectional area of other parts of the temperature homogenizing chamber; said temperature homogenizing chamber is configured for turbulating and blending said first and second parts of said flow with admixed surrounding gaseous medium; said temperature homogenizing chamber comprises a housing connected to said output terminal of said main conduit and an output aperture for discharging a heated, homogenized and disinfected gaseous medium into surrounding media.

3. A blow heater for heating and disinfecting a gaseous medium containing viruses and bacteria therewithin; said blow heater comprising: a. a main conduit having an input terminal and an output terminal; said main conduit having a first aperture defined by a main wall of said main conduit; b. an internal conduit having a second aperture defined by an internal wall of said internal conduit; c. a first impeller configured for blowing said gaseous medium via said internal conduit; d. a heater mounted in said internal conduit by mounting means; said heater being configured for heating to a controlled temperature and disinfecting a first part said gaseous medium; said second aperture is smaller than said first aperture such that said internal conduit is mounted within said main conduit; said input terminal of said main conduit is near a cold zone of said internal conduit; wherein said internal conduit comprises a throat portion is located downstream to said heater; said throat portion has at least one side aperture in said internal wall such that a surrounding gaseous medium from said main conduit is drawn into said throat portion by Venturi pumping and said gaseous medium from said main conduit is admixed to heated and disinfected gaseous medium within said throat portion; said throat portion is connected to a temperature homogenizing chamber disposed downstream to said throat portion such that heated and disinfected gaseous medium mixed with said surrounding gaseous medium flows thereto; said temperature homogenizing chamber disposed downstream to said throat portion; said temperature homogenizing chamber is configured for turbulating and blending said mixed gaseous medium generated in the throat portion; said temperature homogenizing chamber comprises a housing connected to said output terminal of said main conduit and an output aperture for discharging a heated and disinfected gaseous medium into surrounding media.

4. A blow heater for heating and disinfecting a gaseous medium containing viruses and bacteria therewithin; said blow heater comprising: a. a main conduit having an input terminal and an output terminal; said main conduit having a first aperture defined by a main wall of said main conduit; b. an internal conduit having a second aperture defined by an internal wall of said internal conduit; said second aperture is smaller than said first aperture such that said internal conduit is mounted within said main conduit; c. a heater mounted in said internal conduit by mounting means; said heater being configured for heating to a controlled temperature and disinfecting a first part said gaseous medium; d. a first impeller configured for blowing said gaseous medium via said internal conduit; e. a second part of said gaseous medium flows within a space between said walls of said internal conduit and said main conduit is conducted without contacting the heater while the first part of said flow conducted by said internal conduit is heated by said heater; a second impeller configured for blowing said second part of gaseous medium via said space between said walls of said internal conduit and said main conduit; said second impeller is placed in an opening in the main conduit positioned near the cold zone of the internal conduit; wherein said blow heater further comprises a temperature homogenizing chamber disposed downstream to said output terminal of said main conduit; said temperature homogenizing chamber is configured for turbulating and blending said first and second parts of said flow with each other; said temperature homogenizing chamber comprises a housing connected to said output terminal of said main conduit and an output aperture for discharging a heated, homogenized and disinfected gaseous medium into surrounding media.

5. The blow heater according to any one of claims 1 to 4, wherein said temperature homogenizing chamber comprises a 3d turbulating structure configured for blending different parts of said flow of said gaseous medium and homogenizing the temperature of said heated and disinfected gaseous medium before discharging from said output aperture.

6. The blow heater according to any one of claims 1 to 4, wherein said 3d turbulating structure comprises at least one element selected from the group consisting of a plate-like turbulating element angularly disposed relative to a homogenized flow, an aperture disposed along a flow of said heated and disinfected gaseous medium, an open pore lattice-like structure, a freely rotatable propeller and any combination thereof.

7. The blow heater according to any one of claims 1 to 4, wherein said 3d turbulating structure is made of a refractory material.

8. The blow heater according to any one of claims 1 to 4, wherein said mounting means comprises at least one tie-rod securing said internal conduit to the main conduit and securing impellers and propeller to the main and internal conduits.

9. The blow heater according to any one of claims 1 to 4 comprising at least one temperature sensor and a controller configured for monitoring temperature of a heated flow and controlling operation parameters of said heater and impeller

10. The blow heater according to any one of claims 1 to 4 and 9 comprising at least one flow meter and a controller configured for monitoring gaseous flow rate and controlling operation parameters of said heater and impeller.

11. The blow heater according to claims 1 to 4 and 9 with the heater consisting of a plurality of heating elements mounted apart inside the internal conduit.

12. The blow heater according to claims 1 to 4, 10 and 11 with the power supplied to the heating elements is controlled by the signals from at least one temperature sensor and at least one flow meter.

13. The blow heater according to claims 9 and 11, wherein said controller is configured for energizing said heating elements such that power radiated by said heating elements heat said gaseous medium up to temperature thereof detected by said temperature sensor which is effective for disinfecting said gaseous medium.

14. The blow heater according to claim 12, wherein said controller is configured for energizing said heating elements such that power radiated by said heating elements heat said gaseous medium up to temperature thereof detected by said temperature sensor which is effective for disinfecting said gaseous medium at detected flow rate by said flow rate sensor.