WO2009078496A1

WO2009078496A1 - Low pressure closed type boiler and the control method thereof

Info

Publication number: WO2009078496A1
Application number: PCT/KR2007/006556
Authority: WO
Inventors: Tae Sik Min
Original assignee: Kyungdong Navien Co., Ltd.
Priority date: 2007-12-14
Filing date: 2007-12-14
Publication date: 2009-06-25

Abstract

Disclosed is a low pressure air closed-type boiler which has a simple structure and can be installed in both an upward and downward pipe structure, and a control method thereof. The boiler includes: an expansion tank for storing space heating returning water introduced from a space heating pipe to supply the space heating returning water to a heat exchanger by a circulation pump, the expansion tank being interrupted with the air; a pressure sensor installed on an upper portion of the expansion tank and detecting a pressure difference between a pressure of an inside expansion tank and the air pressure; an air open/close valve installed on the upper portion of the expansion tank and discharging the air in the inside expansion tank; and a controller for controlling the open/close valve to be open or closed depending on the pressure of the inside expansion tank detected in the pressure sensor.

Description

LOW PRESSURE CLOSED TYPE BOILER AND THE CONTROL METHOD THEREOF

Technical Field

[1] The present invention relates to a low pressure air closed- type boiler and a control method thereof, and more particularly to a low pressure air closed-type boiler which has a simple structure and can be installed in both an upward pipe and a downward pipe structure, and a control method thereof. Background Art

[2] In general, a boiler can be classified into two types depending on a structure of an expansion tank in which space heating water is stored; an air open-type boiler and an air closed-type boiler.

[3] FIG. 1 is a schematic view illustrating a conventional air open-type boiler and FIG.

2 is a schematic view illustrating a conventional air closed-type boiler.

[4] Referring to FIG. 1, the air open-type boiler has an expansion tank 11 open to the air. Therefore, when a space heating pipe 19 is installed higher than the expansion tank 11 (hereinafter called "upward pipe"), the water in the expansion tank 11 overflows due to water head pressure. Therefore, the air open-type boiler has a general problem of an installation condition that the heating pipe 19 should be installed lower than the expansion tank 11.

[5] Further, the air open-type structure causes an increase of a quantity of dissolved air in the pipe so that the air included in water of the pipe not only increases a fluid noise due to cavitation of a circulation pump 15, but also accelerates oxide erosion of a heat exchanger 16 and the space heating pipe 19 of the boiler, thereby resulting in the deterioration of the durability of the boiler.

[6] However, the air open-type structure boiler is operated in a state of low air pressure so that the expansion tank 11 and other inner pipe of the boiler can be made of a general material, including a sort of a hose made of plastics and rubbers, or the like, and thus a simple and inexpensive structure can be achieved.

[7] Non-described reference numbers 12 and 13 denote space heating returning pipes,

17 denotes a burner, and 18 denotes a blower.

[8] Referring to FIG. 2, the air closed-type boiler has a pressure expansion tank 21 interrupted with the air so that the water does not overflow, even when a space heating pipe 29 is installed higher than the expansion tank 21, i.e. the upward pipe. That is, when the boiler is operated, the temperature inside the pipe becomes high, and the volume is increased, the pressure inside of the pipe is increased and a diaphragm 21a and a nitrogen filler 21b of the expansion tank 21 absorb the pressure.

[9] Therefore, the structure interrupted with the air decreases the quantity of the dissolved oxygen in the pipe, thereby advantageously preventing the erosion of a heat exchanger 26 and the pipe and enhancing the durability.

[10] However, an operating pressure of the air closed-type boiler is high, about l~3kgf/D, so that the expansion tank 21, other pipes 23 and 29 of the boiler, a connecting part, or the like, should be made of materials (typically metallic materials) and structures sufficiently resistant to the pressure. Further, in preparation for a case that the pressure in the pipe becomes excessively high, when the pressure in the pipe is equal to or higher than a predetermined pressure, i.e. 3.5kgf/D in general, an over-pressure safety valve 22 which can discharge the water in the pipe so as to decrease the pressure should be certainly provided. Further, an airvent 24 should be installed in order to remove the air in the pipe generated upon the boiler being initially operated.

[11] Therefore, not only that the structure of the air closed- type boiler is complex, but also the substantially bulky closed-type expansion tank 21 (typically 6-8 liter) should be installed in the air closed-type boiler, so that the boiler becomes disadvantageously heavy and the manufacturing cost thereof is increased.

[12] Non-described reference number 25 denotes a circulation pump, 27 denotes a burner, and 28 denotes a blower. Disclosure of Invention

Technical Problem

[13] Therefore, the present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to provide a low pressure air closed-type boiler which, through combining the conventional air open-type boiler with the conventional air closed-type boiler, has a simple structure, can maintain the pressure of the inside the pipe to be low, and can be employed in both an upward pipe and a downward pipe. Technical Solution

[14] To accomplish the above objects, there is provided a low pressure air closed-type boiler, including: an expansion tank for storing space heating returning water introduced from a space heating pipe in order to supply the space heating returning water to a heat exchanger by a circulation pump, the expansion tank being interrupted with the air; a pressure sensor installed on an upper portion of the expansion tank and detecting a pressure difference between a pressure of an inside expansion tank and the air pressure; an air open/close valve installed on the upper portion of the expansion tank and discharging the air in the inside expansion tank; and a controller for controlling the open/close valve to be open when the pressure of the inside expansion tank detected in the pressure sensor is equal to or higher than the a predetermined pressure and controlling the air open/close valve to be closed when the pressure of the inside expansion tank is lower than the predetermined pressure due to opening of the air open/close valve.

[15] Here, a water-level sensor is installed on one side of a lower portion of the expansion tank and detects the pressure variable depending on a change of the water level of space heating water stored in the expansion tank.

[16] Further, the controller controls whether to open or close the air open/close valve based on water level information detected in the water-level sensor and pressure information detected in the pressure sensor.

[17] To accomplish the above objects, there is provided a method for controlling a low pressure air closed-type boiler, including the steps of: supplying water to an expansion tank until a water level in the expansion tank reaches a predetermined water level when the water is out or insufficient an inside space heating pipe, wherein an air open/close valve installed on an upper portion of the expansion tank is in a closed state; operating the boiler so as to perform the burning by a signal of a controller controlling the air open/close valve; detecting a fact that a pressure of an inside the expansion tank is equal to or higher than a predetermined pressure due to the burning by a pressure sensor installed in the expansion tank, transmitting the fact to the controller, and opening the air open/close valve by the controller; and detecting a fact that a pressure of the inside the expansion tank is lowered than a predetermined pressure due to opening of the air open/close valve by the pressure sensor, transmitting the fact to the controller, and closing the air open/close valve by the controller.

Advantageous Effects

[18] As described above, the low pressure air closed- type boiler and the control method thereof can be employed in the structure of both the upward pipe and the downward pipe by mounting the closed-type expansion tank in contrast to the conventional air open-type boiler and can greatly decrease the amount of time during which the water of the pipe contacts the air so as to decrease the quantity of dissolved air in the pipe, thereby advantageously preventing oxide erosion of the heat exchanger and the space heating pipe, and enhancing the durability.

[19] Further, the low pressure air closed- type boiler is operated with relatively lower pressure rather than the conventional air closed-type boiler so that the boiler can be mounted with the expansion tank and the pipe made of the plastic material, thus decreasing the manufacturing cost of the boiler. Brief Description of the Drawings

[20] FIG. 1 is a schematic view illustrating a structure of a conventional air open-type boiler;

[21] FIG. 2 is a schematic view illustrating a structure of a conventional air closed- type boiler; and

[22] FIG. 3 is a schematic view illustrating a structure of a boiler according to an exemplary embodiment of the present invention. Mode for the Invention

[23] Hereinafter, an exemplary embodiment of the present invention will be described with reference to the accompanying drawings. In the following description and drawings, the same reference numerals are used to designate the same or similar components, and so repetition of the description on the same or similar components will be omitted.

[24] FIG. 3 is a schematic view illustrating a structure of the boiler according to an exemplary embodiment of the present invention.

[25] In the boiler according to the present invention, space heating is performed through a space heating pipe 190 and space heating returning water introduced into an expansion tank 110 through a space heating returning pipe 191 is supplied to a space heating returning pipe 192 and a heat exchanger 160 by a circulation pump 150, which is a structure identical to that of a conventional boiler. Further, the boiler according to the present invention includes a burner 170 for performing combustion through generation of a flame and a blower 180 for providing the air required for the combustion, which are also identical to those of the conventional boiler.

[26] The expansion tank 110 has a structure interrupted with the air, whereby the water stored inside the expansion tank 110 does not overflow even when employed in the structure of an upward pipe. Further, the expansion tank 110 may be made of either synthetic resins or a metallic material. However, when considering the manufacturing cost, it is preferred that the expansion tank 110 is made of the material of synthetic resins.

[27] A pressure sensor 120 for detecting the difference between the pressure of an inner space 110a of the expansion tank 110 and the air pressure is installed at one side of an upper portion of the expansion tank 110.

[28] An air open/close valve 130 is installed on an upper portion of the expansion tank

110 opposite to the pressure sensor 120 in order to discharge the air and decrease the pressure of the inner space 110a when the pressure of the inner space 110a of the expansion tank 110 is increased due to the operation of the boiler. The air open/close valve 130 can include an on/off valve open or closed by the electric power.

[29] The pressure sensor 120 and the air open/close valve 130 are connected to a controller (not shown). The controller controls the air open/close valve 130 to be open when the pressure of the inner space 110a of the expansion tank 110 detected in the pressure sensor 120 is equal to or higher the predetermined pressure, and controls the air open/close valve 130 to be closed when the pressure of the inner space 110a of the expansion tank 110 detected in the pressure sensor 120 is lower than the predetermined pressure due to opening of the air open/close valve 130.

[30] In this case, it is preferred that the pressure predetermined in the controller as a reference determining opening or closing the air open/close valve 130 is set considering the floor height of a residential building.

[31] That is, assuming that the floor height of a general residential building is 3m, the floor height of the three-floor building is 10m. When the boiler with the upward pipe structure is installed in the building, the maximum water head pressure applied to the inside the pipe is about lkgf/D. Therefore, it is preferred that the maximum permissible pressure of the inner space 110a of the expansion tank 110 is set to be lkgf/D and the air open/close valve 130 is opened when the pressure reaches the maximum permissible pressure. As such, when the maximum permissible pressure of the inner space 110a of the expansion tank 110 is determined, the maximum permissible height of the floor in the upward pipe structure is limited depending on the predetermined value.

[32] In the meantime, it is preferred that a water-level sensor 140 is installed on the expansion tank 110. The water-level sensor 140, for an example, can include a sensor installed on a middle part of the inside the expansion tank 110 and determining the level of the space heating water to be a specific water level when the level of the space heating water rises to be in contact with the sensor.

[33] However, in the present invention, it is preferred that the controller considers the pressure information detected in the pressure sensor 120 together with the water level information detected in the water-level sensor 140 so as to determine whether to open or close the air open/close valve 130. Therefore, the water-level sensor 140 can be installed on one side of a lower portion of the expansion tank 110 so as to consecutively detect the pressure variable depending on a change of the water level of the space heating water stored in the expansion tank 110.

[34] Hereinafter, a control method of the present invention having the above configuration will be described.

[35] First, when the water is out or insufficient in the inside the space heating pipe installed with the upward pipe or the downward pipe structure, the water-level sensor 140 detects it and an automatic water supply valve (not shown) supplies the water to the expansion tank 110 until the level of the water in the expansion tank reaches an appropriate water level. At this time, the air open/close valve 130 comes to the 'closed' state. [36] Under this state, when the boiler is operated/burned, the volume is increased according to the rising of the temperature of the water so as to raise the water level of the inside the expansion tank 110 such that the air of the inner space 110a of the expansion tank 110 is compressed so as to increase the pressure.

[37] As described above, when the pressure becomes high and the pressure detected in the pressure sensor 120 is equal to or higher than the pressure (lkgf/D in the present embodiment) predetermined in the controller, the controller transmits the signal for the air open/close valve 130 to be an 'open' state.

[38] When the air open/close valve 130 opens to discharge the air, the pressure in the inner space 110a of the expansion tank 110 becomes low, and the pressure sensor 120 detects that the pressure in the inner space 110a of the expansion tank 110 becomes equal to or lower than the pressure (e.g., O.5kgf/D) predetermined in the controller, the controller transmits the control signal for the air open/close valve 130 to be a 'closed' state.

[39] In this state, when the temperature of the boiler reaches the predetermined temperature so as to stop the burning, the temperature of the space heating water becomes gradually low such that the water level of the inside the expansion tank 110 is lowered. As a result, the volume of the inner space 110a of the expansion tank 110 is increased so that the pressure is decreased. Depending on cases, the pressure of the inner space 110a of the expansion tank 110 may be the negative pressure lower than the air pressure.

[40] As described above, when the pressure of the inner space 110a of the expansion tank 110 is lowered by the first one-time open of the air open/close valve 130, it is possible to absorb the up-and-down change of the pressure of the inner space 110a of the expansion tank 110 variable within the predetermined pressure range even though the air open/close valve 130 is not opened again when the operation and stoppage of the boiler is repeated,. Therefore, the operating principle of the boiler according to the present is identical to that of the conventional air closed-type boiler so that the water is prevented from the contact to the air, thereby preventing the oxygen erosion of the space heating pipe and the deterioration of the durability caused by the dissolved air in the water.

[41] While this invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiment and the drawings, but, on the contrary, it is intended to cover various modifications and variations within the spirit and scope of the appended claims. Industrial Applicability [42] As such, the present invention provides a low pressure air closed-type boiler which, through combining the air open-type boiler with the air closed-type boiler, has a simple structure, can maintain the pressure of the inside the pipe to be low, and can be employed in both an upward pipe and a downward pipe.

[43]

[44]

Claims

[1] L A low pressure air closed- type boiler, comprising: an expansion tank for storing space heating returning water introduced from a space heating pipe in order to supply the space heating returning water to a heat exchanger by a circulation pump, the expansion tank being interrupted with the air; a pressure sensor installed on an upper portion of the expansion tank and detecting a pressure difference between a pressure of an inside expansion tank and the air pressure; an air open/close valve installed on the upper portion of the expansion tank and discharging the air in the inside expansion tank; and a controller for controlling the open/close valve to be open when the pressure of the inside expansion tank detected in the pressure sensor is equal to or higher than the a predetermined pressure and controlling the air open/close valve to be closed when the pressure of the inside expansion tank is lower than the predetermined pressure due to opening of the air open/close valve.

[2] The low pressure air closed-type boiler as claimed in claim 1, wherein a water- level sensor is installed on one side of a lower portion of the expansion tank and detects the pressure variable depending on a change of the water level of space heating water stored in the expansion tank.

[3] The low pressure air closed-type boiler as claimed in claim 2, wherein the controller controls whether to open or close the air open/close valve based on water level information detected in the water-level sensor and pressure information detected in the pressure sensor.

[4] A method for controlling a low pressure air closed-type boiler, comprising the steps of: supplying water to an expansion tank until a water level in the expansion tank reaches a predetermined water level when the water is out or insufficient an inside space heating pipe, wherein an air open/close valve installed on an upper portion of the expansion tank is in a closed state; operating the boiler so as to perform the burning by a signal of a controller controlling the air open/close valve; detecting a fact that a pressure of an inside the expansion tank is equal to or higher than a predetermined pressure due to the burning by a pressure sensor installed in the expansion tank, transmitting the fact to the controller, and opening the air open/close valve by the controller; and detecting a fact that a pressure of the inside the expansion tank is lowered than a predetermined pressure due to opening of the air open/close valve by the pressure sensor, transmitting the fact to the controller, and closing the air open/ close valve by the controller.