Graphite is produced from powder as a carbon source by means of a graphitization furnace. The graphitization furnace is comprised of: an electrically conductive crucible including a hollow configured to house the powder; an electrode including a columnar shaft and a head provided at an end of the shaft, the head having a shape selected from the group consisting of a sphere, a hemisphere, a column with a rounded edge, a cone, and a cone with a rounded tip; and a power source configured to apply electric current to the powder through the crucible and the electrode.

A liquid heater such as a direct electrical resistance liquid heater having multiple flow channels is provided with a temperature-sensing element in the form of a wire extending across numerous channels, preferably all of the channels, near the downstream ends of the channels. The resistance of the wire represents the average temperature of the liquid passing through all of the channels, and hence the temperature of the mixed liquid exiting from the heater. A bubble suppressing structure is provided in the vicinity of the wire.

A method and a device for closed-loop control of an electrode gap in a vacuum arc furnace subjects an electrode gap of a melting electrode from the surface of a melt material to closed-loop control as a function of a droplet short-circuit rate. For this purpose, a histogram of detected droplet short-circuits is created on the basis of at least one droplet short-circuit criterion. The histogram is subdivided into sub-areas, a characteristic sub-area of the histogram is selected for closed-loop control purposes. The electrode gap is subjected to closed-loop control on the basis of the droplet short-circuits which can be associated with the selected sub-area.

Circuit arrangement (1) for an electric heater, in particular an electric fluid heater (12), for use in a vehicle, comprises a connection for providing a voltage, in particular a high-voltage, wherein the connection has a first connection pole (HV+) for a first operating voltage potential and a second connection pole (HV) for a second operating voltage potential, a heating resistor (R.sub.H) which is configured to convert a current flowing through the heating resistor (R.sub.H) into heat, when the voltage is applied, an electronic switch (S1) which is connected in series with the heating resistor (R.sub.H) between the first connection pole (HV+) and the second connection pole (HV), a control device (42) which is connected to the electronic switch (S1) and is configured to operate the switch (S1) in a pulsed manner in order to set a heating power of the electric fluid heater (12), and an input capacitor (C1) which is connected in parallel with the series-connected heating resistor (R.sub.H) and switch (S1) between the first connection pole (HV+) and the second connection pole (HV). The heating resistor (R.sub.H) includes a first partial resistor (R1) and a second partial resistor (R2) that are connected in series and define a center tap (34, 36, 38) between them. The circuit arrangement (1) also has an additional capacitor (C2) which is connected between the center tap and the second connection pole (HV).

Circuit arrangement (1) for an electric heater, in particular an electric fluid heater (12), for use in a vehicle, comprises a connection for providing a voltage, in particular a high-voltage, wherein the connection has a first connection pole (HV+) for a first operating voltage potential and a second connection pole (HV) for a second operating voltage potential, a heating resistor (R.sub.H) which is configured to convert a current flowing through the heating resistor (R.sub.H) into heat, when the voltage is applied, an electronic switch (S1) which is connected in series with the heating resistor (R.sub.H) between the first connection pole (HV+) and the second connection pole (HV), a control device (42) which is connected to the electronic switch (S1) and is configured to operate the switch (S1) in a pulsed manner in order to set a heating power of the electric fluid heater (12), and an input capacitor (C1) which is connected in parallel with the series-connected heating resistor (R.sub.H) and switch (S1) between the first connection pole (HV+) and the second connection pole (HV). The heating resistor (R.sub.H) includes a first partial resistor (R1) and a second partial resistor (R2) that are connected in series and define a center tap (34, 36, 38) between them. The circuit arrangement (1) also has an additional capacitor (C2) which is connected between the center tap and the second connection pole (HV).

An ohmic heater has a structure (20) defining a flow path extending in a downstream direction (D), a first pair of electrodes (34a,34b) and a second pair of electrodes (36a,36b). The electrodes of each pair are adjacent one another in the downstream direction but spaced from one another in a direction perpendicular to the downstream direction; the pairs of electrodes are spaced apart from one another in the downstream direction. An electrical circuit (40,42,44,46,48,50) is operative to apply a voltage (i) between the electrodes (34a,34b) of the first pair; or (ii) between the electrodes (36a,36b) of the second pair; or (iii) between at least one electrode (34a) of the first pair and at least one electrode (36b) of the second pair, and may vary the applied voltage. The heater can meet varying conditions such as changes in conductivity of the liquid flowing through the heater.

A heater for heating a conductive liquid includes a two-dimensional array of rod-like electrodes (22, 122, 322, 422, 522) extending parallel to one another, an electrical power supply having a plurality of poles, and power switches to connect different ones of the electrodes to different poles so that current flows between the poles through the liquid. The array desirably includes outer electrodes defining the boundary (24, 424) of the array and inner electrodes disposed within this boundary. The array may have regular or irregular spacings between the electrodes. The array can provide numerous different connection schemes to vary the electrical resistance between the poles and thus vary the heating rate. The array can be arranged to provide substantially equal currents through three poles of a three-phase power supply.

A heater for heating a conductive liquid includes a two-dimensional array of rod-like electrodes (22, 122, 322, 422, 522) extending parallel to one another, an electrical power supply having a plurality of poles, and power switches to connect different ones of the electrodes to different poles so that current flows between the poles through the liquid. The array desirably includes outer electrodes defining the boundary (24, 424) of the array and inner electrodes disposed within this boundary. The array may have regular or irregular spacings between the electrodes. The array can provide numerous different connection schemes to vary the electrical resistance between the poles and thus vary the heating rate. The array can be arranged to provide substantially equal currents through three poles of a three-phase power supply.

A modular platform electric trench heater is provided. The electric trench heater has a case having a first end and a second end, an electrical heating unit disposed in the case and designed to generate heat and create an upward convection current therethrough, a baffle dividing the case in a longitudinal direction into a first portion and a second portion, wherein the baffle is designed to direct the upward convection current from the first portion of the case to the second portion of the case, and a connecting unit provided in the form of a connecting plate and a plate fixing mechanism that couples the connecting plate to the first end of the case.

A modular platform electric trench heater is provided. The electric trench heater has a case having a first end and a second end, an electrical heating unit disposed in the case and designed to generate heat and create an upward convection current therethrough, a baffle dividing the case in a longitudinal direction into a first portion and a second portion, wherein the baffle is designed to direct the upward convection current from the first portion of the case to the second portion of the case, and a connecting unit provided in the form of a connecting plate and a plate fixing mechanism that couples the connecting plate to the first end of the case.