ELECTRIC ROOM HEATER WITH MAGNETOSTRICTION

Technical Field

The invention belongs to the field of converting electrical energy to heat energy and is intended to heat premises where people reside or for similar purposes. Magnetostriction in technique occurs in core sheets of energy transformers. According to the international classification of patents the IPC mark is: Background Art

Room heating by electrical energy is performed by means of electrical heat sources. In a narrower sense, by similarity, the state of technique at present is represented by the invention PCT/YU2006/000021 with strip heater of oriented cold rolled transformer sheet through which passes alternating electric current. However, lesser magnetostriction in the strip is achieved by lesser density of electric current in order to reduce level of noise because, at that time, it was not discovered that higher magnetostriction increases degree of thermal efficiency of the heat source. Therefore, electric heater with magnetostriction represents innovation of the invention PCT/YU2006/000021. Magnetostriction is increasing coefficient of efficiency close to the level which is achieved by natural air flow around the standard heater at higher temperature, for example fan heater.

Disclosure of Invention

Electric room heater with magnetostriction has a heater in a form of strip of oriented cold rolled transformer sheet. Alternating electric current passes through the strip. Electric current heats the strip and creates variable magnetic field. As the strip is made of Ferro-magnetic material, crystal lattice is subject of deformation during magnetizing. This effect is called magnetostriction and, macroscopically viewed, dimensions of the strip are changed. Rhythm of the strip dimensions change is in compliance with the rhythm of magnetic field variations. Change in the strip dimensions cause vibrations of the surroundings that is of air and emitting of sound waves. If electric current frequency is 50

Hz, sound waves produces first harmonics of 100 Hz and higher harmonics of 200, 400, 800 Hz, and so on. The strip with magnetostriction sets free the heat energy and consequently increases degree of thermal efficiency of the heat source. The speed of air flow is higher and the strip over-temperature is lower. It is assumed that this happens in the fallowing way. Heat energy is part of molecular-kinetic energy and molecular-potential energy which is transmitted from one body to another. Measure of thermal state is temperature. As a rule, heat is transmitted from body of higher temperature to a body of lower temperature in three ways: by conductivity, convection and radiation of heat.

So far as the strip is connected, heat is transmitted to the air by convection and radiation, and strip over-temperature is approximately calculated on the basis of the following equation:

S(p _k +p,) where:

P - electric power of heather S - surface of the strip

P _k - coefficient of heat transmitting by convection Pi- coefficient of heat transmitting by radiation.

When the strip has magnetostriction, strip dimension is changing in the direction of magnetic field strength vector, which is accompanied by changes of dimensions normal to the direction of the field but the strip volume remains almost constant and, consequently, also the strips surface. As a result, lower over-temperature of the strip and higher speed of air flow are related to die deformation of crystal lattice, rhythm of the change of the strip dimensions and vibrations of particles of surrounding air, because heat is a form of transmitting energy that represents multitude of microphysical processes. Analogous to heat transmitting by convection and by radiation, over-temperature of the strip with magnetostriction can be calculated if we introduce coefficient of heat transmitting by magnetostriction and equation will get the following form, i.e.:

δ0 = s(p _k +p, +p _m ) where: P _m - coefficient of heat transmitting by magnetostriction.

Because of the coefficient of magnetostriction the strip over- temperature is lower. That is how out of total electric energy a part for maintaining the strip over-temperature is decreased by magnetostriction and the part that heats the air is increased, and - subsequently - degree of thermal efficiency of the heat source is higher.

According to the invention, the strip heater with magnetostriction is in use and measures consists are taken for decrease level of noise in the structure of the heater. The measures consist in decrease of the number of vibrating elements and connecting elements by welding and elastic coupling to the housing. According to the invention, the level of noise can be lowered even more by use of rectifier but then magnetostriction will be decreased as well because pulsating current is passing through the strip. This is not valid for three-phase rectifier because the frequency of pulsating current is higher. Advantages of this invention are in the fact that certain air temperature in a room is maintained with less electric energy and therefore the heater with magnetostriction is more economic.

Brief Description of Drawings

• Fig. 1 shows curves indicating room air temperature changes when the heat source is: 1 - oil radiator of 3.2 kW, 2 - oil radiator of 2.1 kW, 3 - room heater with magnetostriction of 2.0 kW. • Fig. 2 shows room and positions of thermal sources and thermometer.

• Fig. 3 shows two projections of the heater with magnetostriction.

• Fig. 4 shows elastic coupling of heater support and the housing.

• Fig. 5 shows, in three projections, connection of heater elements by welding and directions of magnetic fluxes through strip heaters.

• Fig. 6 shows rectifier and condenser on supports welded for heater frame.

• Fig. 7 shows electric scheme of coupling the room heater with magnetostriction to alternating current.

• Fig. 8 shows electric scheme of the connection enabling alternating or pulsating electric current to pass through strip heaters.

• Fig. 9 shows pulsating current curve. Q • Fig. 10 shows three-phase connection of strip heater.

Best Mode for Carrying Out of the Invention

Electric room heater with magnetostriction is heat source with better degree of thermal efficiency. Fig. 1 shows experimental results. Curve 1 shows raise of air temperature in a room size 7 - 2O m ³ shown at Fig. 2 when heating is 5 affected by electric oil-radiator in position S, of 3.2 kW. Measuring is performed within time interval of 5 minutes and shown at x-axe. Total measuring time is 40 minutes. At y-axe are temperatures indicated by thermometer 6. Curve 2 shows rise of air temperature in the room when heating is affected by electric oil-radiator, of 2.1 kW. Rise of air temperature is 0 lesser because electric power of the radiator is smaller. Curve 3 shows rise of air temperature in the room when heating is performed by electric room heater with magnetostriction, of 2.0 kW. Curves 1 and 3 cross each other at the point A. As a result, air temperature of 27.6°C is achieved by the heat sources within the same time of 32 minutes although their electric powers are not equal. Since 5 consumed electric energy is proportional to electric power, electric oil-radiator consumed:

3.2 kW/2.0 kW ^• = 1.6 Q more electric energy than the electric energy consumed by electric room heater with magnetostriction.

According to Fig. 1 the air temperature of 24° C was achieved by all of the three heat sources but within different time intervals. Electric room heater with magnetostriction of 2.0 kW, curve 3, achieved the temperature of 24° C in 5 9.5 minutes and consumed electric energy:

2.0 kW*9.5/60 h=0.316 kWh.

Electric oil radiator of 3.2 kW, curve 1, achieved temperature of 24° C within 18 minutes and consumed electric energy:

3.2 kW*18/60 h-0.96 kWh.

Electric radiator of 2.1 IcW, curve 2, achieved temperature of 24° C within 27.5 minutes and consumed electric energy:

2.1 kW*27.5/60h=0.96 kWh.

Electric radiators consumed equal quantity of electrical energy because their degree of thermal efficiency is equal. Electric room heater with magnetostriction consumed less energy: 0.96 kWh/0.316 kWh=3.04 times because of better degree of thermal efficiency. It is pointed out that magnetic strip crosscutting of the heater was 10 mm x 0.27 mm, density of alternating current amounted to 3.3 A/mm ² and the frequency 50 Hz. Outside temperature, when the measuring took place, was for the curve 1: +11° C, for the curve 2: +13° C and for the curve 3: +12° C.

Let the electric oil radiator and electric room heater with magnetostriction maintain, by thermostats, medium room temperature of 23° C ± 1° C. Thermostat of the heater with magnetostrictioo will be switched on during time interval of 4.25 minutes (curve 3), and oil radiator thermostat will be switched on for 9.5 minutes (curve 2). Time intervals when thermostats are switched off, when the room is cooling, are approximately equal and amount to 14.25 minutes (curve 4). If the total of these time intervals is considered to be period of thermostats, then period of the room heater with magnetostriction is equal to:

4.25 minutes + 14.25 minutes = 18.5 minutes, period of the oil radiator thermostat is:

9.5 minutes + 14.25 minutes = 23.75 minutes.

If the room heater and the radiator work 30 days for 14 h per day, that is 25200 minutes, they will make different number of periods. Number of periods of the room heater with magnetostriction is:

25200 minutes/ 18.5 minutes = 1362, number of oil radiator periods amounts to :

25200 minutes/23.75 minutes = 1061.

Room heater with magnetostriction is switched on for 30 days in total: 1362*4.25 minutes=5788 minutes = 96.4 h and electrical energy consumed amounted to:

2.0kW*96.4h = 192.8 kWh, and oil radiator is switched on:

1061*9.5 minutes= 10080 minutes = 168 h with energy consumed : 2.1 kW*168 h = 352.8 kWh.

Consequently, oil radiator consumed:

352.8 kWh/192.8 kWh = 1.82 times more electric energy than the room heater with magnetostriction. The curves indicate that this ratio depends on temperature maintained in the room.

Magnetostriction produces noise. According to the idea of the invention, noise level produced by the room heater is reduced to the level of noise covered by the normal noise in apartments. Fig. 3 shows outside view of electric room heater with magnetostriction and consists of housing 8, blinds for air circulation 9, support 10, electric switch 11, signal bulb 12, thermostat 13 and the connecting cable with wall plug. Walls of the housing 8 are covered from the inside by insulation 15 that has quality of absorbing noise. Housing 8 is connected with the support 16, Fig. 4. Between the housing and the support

16 there is elastic rubber spacer 17 that reduces transmitting vibrations from the support 16 to the housing 8. Strip heaters 18, are contained in the housing 8, Fig. 5. Central supports 19 of the strip heaters 18 are welded by the weld 21 for the frame 20. Magnetic flux 37 created by electric current passing through strip heaters is enclosed by the central supports 19 and the frame 20. The frame

20 is welded by the welding 22 to the supports 16. Next measure, according to the idea of the invention with a view to decrease the noise, is using electric rectifiers. For the frame 20, position 36, as per Fig. 5, plate 23 is welded by the welding 24 to which is fastened a rectifier 25 by a screw. The plate 23 is cooling the rectifier 25 by its surface.

On another side of the frame 20, support 26 is welded by the welding 27. Condenser 28 is fastened by a screw to the support 26, Fig. 6. Fig. 8 shows electric connection diagram enabling - through the switch 29, when in position 1, strip heaters 18 to be switched on to alternating voltage as per the Fig. 7. When the switch is in position 2 the strip heaters 18 are, through the rectifier

25, connected to the alternating voltage. In parallel connection with the strip heaters 18 is situated condenser 28. Now, through the strip heaters is passing

pulsating electric current, with first harmonic of 100 Hz, Fig. 9. Pulsating current creates lesser intensity of magnetostriction and, consequently, noise is lesser. As a consequence of lesser intensity of magnetostriction is a lesser degree of efficiency of thermal energy. Electric power of the strip heaters increases because the rectifier with condenser increases voltage. Appears capacitance reactive component of the current. Cosinus is higher than 0.85.

The room heater with magnetostriction of higher output is realized when switched on to the three-phase. Fig. 10 shows electric connection diagram. The strip heaters 18 are coupled through a three-phase bridge connected rectifier 33, three-phase thermostat 32 and three-phase switch 31 with three-phase vohage. Direct pulsating current is passing through strip heaters 18. As the first harmonic of pulsating current is 300 Hz, magnetostriction is created for better efficiency of thermal energy. When the switch 34 is on, the condenser 35 is switched on, magnetostriction and the level of noise are reduced, however the degree of efficiency as well.