DESC:FORM 2

THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENT RULES, 2003

COMPLETE SPECIFICATION
(See Section 10 and Rule 13)

Title of invention:
A SYSTEM FOR CLEANING A HEAT EXCHANGER

Applicant:
Mazagon Dock Shipbuilders Limited
A company Incorporated in India under the Companies Act, 1956
Under Ministry of Defence,
(A Govt. of India Undertaking)
Having address:
Dockyard Road, Mazagon,
Mumbai - 400010, Maharashtra, India

The following specification particularly describes the invention and the manner in which is to be performed.

CROSS-REFERENCE TO RELATED APPLICATIONS AND PRIORITY
[001] The present application claims priority from Indian provisional application no. 201921019346 filed on 15th May 2019.
TECHNICAL FIELD
[002] The present subject matter described herein, in general, relates to a system for cleaning of heat exchanger. More particularly, the system relates to cleaning of heat exchanger by back flushing.
BACKGROUND
[003] Thermal energy systems incorporating heat exchangers typically comprise a primary loop, from which heat is removed, and a secondary loop, to which heat is transferred. The heat exchanger transfers heat between the primary and the secondary loop. A heat transfer fluid is circulated through the primary loop, for removing heat from, the primary side of the heat exchanger. A secondary fluid to which heat is transferred flows through the secondary side of the heat exchanger. The primary and secondary sides of the heat exchanger typically have numerous small passageways in close association through which the fluids flow, which facilitate the transfer of thermal energy between the primary side and the secondary side. Generally, the primary fluid used in heat exchangers is a synthetic coolant while the secondary fluid used is water obtained from natural streams, river water, sea water etc. Since the secondary fluid i.e. water used in the heat exchanger is derived from natural streams, river or sea, there is a high probability of deposition of silt, mud or foreign materials in the heat exchanger. Deposition of the silt, mud or foreign materials in the heat exchanger, reduces the passage available for flow of secondary fluid, thereby reducing the flow rate of the secondary fluid. As a result, the heat transfer rate between the primary fluid and the secondary fluid is considerably reduced, leading to increase in temperature of the primary fluid. Thus, there is substantial drop in performance of the system, which is undesirable. Hence, the operator is forced to stop the operation of the heat exchanger for maintenance. Conventionally, the maintenance of the heat exchanger is carried out only after stopping operation of the heat exchanger system, resulting in long break down hours, which hampers the productivity. Hence, there is a need to devise a system for maintenance of the heat exchanger, without stopping the operation of the heat exchanger.
SUMMARY
[004] Before the present system and method are described, it is to be understood that this application is not limited to the particular machine or an apparatus, and methodologies described, as there can be multiple possible embodiments that are not expressly illustrated in the present disclosures. It is also to be understood that the terminology used in the description is for the purpose of describing the particular versions or embodiments only, and is not intended to limit the scope of the present application. This summary is provided to introduce aspects related to a system for back flushing a heat exchanger, and the aspects are further elaborated below in the detailed description. This summary is not intended to identify essential features of the proposed subject matter nor is it intended for use in determining or limiting the scope of the proposed subject matter.
[005] The proposed invention discloses a system for cleaning a heat exchanger. The system comprises a heat exchanger configured to transfer heat from a primary fluid circulated through a primary loop to a secondary fluid circulated through a secondary loop. The secondary loop comprises a secondary fluid inlet port valve and a secondary fluid outlet port valve to control flow of the secondary fluid in the secondary loop along a first direction during regular operation of the heat exchanger. Further, the system comprises a back flushing circuit configured to input flow of pressurized water from a fire main line along a second direction through a pressurized water inlet connection into the secondary loop of the heat exchanger and output the pressurized water from the secondary loop through a back flush water outlet connection into the drain tank during back flushing operation of the heat exchanger. Furthermore, the back flushing circuit comprises a shut off ball valve fitted on the pressurized water inlet connection and a shut off ball valve fitted on the back flush water outlet connection.
[006] In one aspect of the present invention, the secondary fluid inlet port valve and the secondary fluid outlet port valve are kept in open position to facilitate flow of secondary fluid through the secondary loop of the heat exchanger in a first direction during regular operation of the heat exchanger. Further, during regular operation of the heat exchanger, the shut off ball valve and the shut off ball valve are kept in closed position to prevent entry of pressurized water into the secondary loop of the heat exchanger.
[007] In another aspect of the present invention, a secondary fluid inlet port valve and a secondary fluid outlet port valve are kept in closed position to prevent of secondary fluid into the secondary loop during back flushing operation of the heat exchanger. Further, a shut off ball valve and a shut off ball valve are kept in open position to facilitate flow of pressurized water from the fire main line into the secondary loop of the heat exchanger in a second direction during back flushing operation of the heat exchanger.
[008] The present subject matter described herein, in general, relates to a system for back flushing of heat exchangers.
[009] The present subject matter described enables cleaning or overhauling of heat exchangers, without stopping the operation of the heat exchanger.
[0010] The present subject matter described prevents loss of breakdown hours.
[0011] The present subject matter described prevents frequent opening or dismantling of heat exchanger for cleaning or overhauling purpose.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The foregoing summary, as well as the following detailed description of embodiments, is better understood when read in conjunction with the appended drawing. For the purpose of illustrating the disclosure, there is shown in the present document example constructions of the disclosure, however, the disclosure is not limited to the specific methods and apparatus disclosed in the document and the drawing.
[0013] The detailed description is described with reference to the accompanying figure. In the figure, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawing to refer like features and components.
[0014] Figure 1 illustrates a system configured for regular operation of heat exchanger, in accordance with an embodiment of the present subject matter.
[0015] Figure 2 illustrates a system configured for cleaning of heat exchanger, in accordance with an embodiment of the present subject matter.
[0016] The figure depicts various embodiments of the present disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following discussion that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.
DETAILED DESCRIPTION
[0017] Some embodiments of this disclosure, illustrating all its features, will now be discussed in detail. The words "comprising", “having”, and "including," and other forms thereof, are intended to be equivalent in meaning and be open ended in that an item or items following any one of these words is not meant to be an exhaustive listing of such item or items, or meant to be limited to only the listed item or items. Although any systems and methods similar or equivalent to those described herein can be used in the practice or testing of embodiments of the present disclosure, the exemplary, systems and methods are now described. The disclosed embodiments are merely exemplary of the disclosure, which may be embodied in various forms.
[0018] Various modifications to the embodiment will be readily apparent to those skilled in the art and the generic principles herein may be applied to other embodiments. However, one of ordinary skill in the art will readily recognize that the present disclosure is not intended to be limited to the embodiments illustrated, but is to be accorded the widest scope consistent with the principles and features described herein.
[0019] Thermal energy systems incorporating heat exchangers typically comprise a primary loop, from which heat is removed, and a secondary loop, to which heat is transferred. The heat exchanger transfers heat between the primary and the secondary loop. A heat transfer fluid is circulated through the primary loop, for removing heat from, the primary side of the heat exchanger. A secondary fluid to which heat is transferred flows through the secondary side of the heat exchanger. The primary and secondary sides of the heat exchanger typically have numerous small passageways in close association through which the fluids flow, which facilitate the transfer of thermal energy between the primary side and the secondary side. Generally, the primary fluid used in heat exchangers is a synthetic lubricating oil or lubricant while the secondary fluid used is water obtained from natural streams, river water, sea water etc. Since the secondary fluid i.e. water used in the heat exchanger is derived from natural streams, river or sea, there is a high probability of deposition of silt, mud or foreign materials in the heat exchanger. Deposition of the silt, mud or foreign materials in the heat exchanger, reduces the passage available for flow of secondary fluid, thereby reducing the flow rate of the secondary fluid. As a result, the heat transfer rate between the primary fluid and the secondary fluid is considerably reduced, leading to increase in temperature of the primary fluid. Thus, there is substantial drop in performance of the system, which is undesirable. Hence, the operator is forced to stop the operation of the heat exchanger for maintenance. Conventionally, the secondary loop of the heat exchanger is cleaned only after stopping operation of the system, resulting in long break down hours.
[0020] The present invention proposes a system that overcomes the shortcomings of the prior art. The proposed system enables cleaning of the heat exchanger without stopping the regular operation of the heat exchanger.
[0021] Referring now to figure 1, in one aspect of present invention, a system configured for regular operation of heat exchanger (1) is disclosed. The heat exchanger (1) comprises a primary fluid inlet port (2), a primary fluid outlet port (3), a secondary fluid inlet port valve (4) and a secondary fluid outlet port valve (5). The heat exchanger (1) comprises a primary loop and a secondary loop wherein primary loop circulates the primary fluid, which is a synthetic lubricating oil or lubricant while the secondary loop circulates secondary fluid i.e. water obtained from natural streams, river water, sea water etc. The primary fluid inlet port (2) and the primary fluid outlet port (3) form a part of primary loop of the heat exchanger (1) whereas the secondary fluid inlet port valve (4) and the secondary fluid outlet port valve (5) form a part of secondary loop of the heat exchanger (1). The secondary fluid inlet port valve (4) and the secondary fluid outlet port valve (5) are configured to control the flow of the secondary fluid in the secondary loop of the heat exchanger (1). An enclosure comprises a hollow tubular structure to form a secondary loop wherein the primary loop passes through said secondary loop for heat exchange. The primary loop of the heat exchanger (1) is positioned in close proximity with the secondary loop and the high temperature source whose temperature is required to be maintained within the permissible limits. The primary fluid i.e. lubrication oil or lubricant absorbs the heat from the engine and said heated primary fluid flows through the primary loop towards the primary fluid inlet port (2) of the heat exchanger (1). The primary fluid i.e. lubrication oil or lubricant is circulated in a closed loop circuit. Thus, when the lubricant flows from the primary fluid inlet port (2) towards the primary fluid outlet port (3) of the primary loop of the heat exchanger (1), it rejects heat absorbed from the high temperature source to the low temperature source that is the secondary fluid of the secondary loop of the heat exchanger. Due to absorption of heat at engine by the circulated lubricant, the temperature of the high temperature source is maintained or reduces whereas the temperature of the lubricant rises. The secondary loop of the heat exchanger (1) uses secondary fluid such as water obtained from natural streams, river water, sea water etc. in open loop circuit. The temperature of the secondary fluid i.e. water obtained from the above mentioned sources is much lower than the high temperature source or the heated lubricant. When the heated lubricant flows towards the primary fluid outlet port (3) of the primary loop of the heat exchanger (1), the secondary fluid i.e. water flowing through the secondary loop of the heat exchanger (1) absorbs the heat of the heated lubricant. Thus, the temperature of the heated lubricant flowing through the primary loop of the heat exchanger (1) reduces whereas the temperature of the secondary fluid increases. The lubricant in the primary loop is now again circulated towards the engine from the heat exchanger (1) to continue the cycle of heat removal from the heat source.
[0022] Due to use of secondary fluid i.e. water from natural streams, river or sea, there is deposition of slit, mud or foreign materials in the heat exchanger (1), leading to drop in efficiency of the heat exchanger (1) and the overall system. Conventionally, the operation of the heat exchanger needs to be stopped for cleaning the deposited slit, mud or foreign materials. The present invention proposes a system for cleaning the secondary loop of the heat exchanger by back flushing, without stopping the operation of the heat exchanger.
[0023] Referring now to figure 2, in one aspect of present invention, a system for cleaning of heat exchanger (1) is disclosed. The system for cleaning the heat exchanger (1) comprises a flushing circuit. The flushing circuit is configured to flush highly pressurized fluid for cleaning the inner surface of the secondary loop and the outer surface of the primary loop in the heat exchanger (1). The flushing circuit comprises a highly pressurized fluid inlet connection (8) and a flush fluid outlet connection (9) connected to the secondary loop of the heat exchanger (1). The pressurized fluid inlet connection (8) is connected at the outlet of the secondary loop of the heat exchanger (1) and comprises a pressurized water source from a fire main line. Further, the pressurized fluid inlet connection (8) is fitted with a flow control valve (6) to permit, restrict or control flow of pressurized water from the fire main line into the secondary loop of the heat exchanger (1) for back flushing during maintenance. The flush fluid outlet connection (9) is connected at the inlet of the secondary loop of the heat exchanger (1). Further, the flush fluid outlet connection (9) is fitted with a flow control valve (7) to permit, restrict or control flow of back flushed water from the secondary loop of the heat exchanger (1) to a drain tank. Thus, the flushing circuit is configured with a highly pressurized fluid inlet connection (8) and a flush fluid outlet connection (9) connected to the secondary loop of the heat exchanger (1) to facilitate flushing of highly pressurized fluid from a fluid source along a second direction for cleaning the enclosure of heat exchanger (1). The flushing circuit is configured with the first flow control valve (6) and the second flow control valve (7) mounted on the highly pressurized fluid inlet connection (8) and flush fluid outlet connection (9) respectively to control flow of highly pressurized fluid along the second direction. The second direction can be defined as flow of pressurized fluid from the enclosure outlet point (10) towards the enclosure inlet point (11). Further, the flushing circuit also referred to as a back flushing circuit is configured to remove deposited slit, mud or foreign material from the enclosure of the heat exchanger (1) by flushing highly pressurized fluid. The flow control valve (6) and flow control (7) are configured from one of a ball valve, a gate valve or a globe valve.
[0024] During regular operation of the heat exchanger (1), the secondary fluid i.e. water flows in a first direction in an open loop circuit as the secondary fluid inlet port valve (4) and the secondary fluid outlet port valve (5) are kept in open position whereas the first flow control valve (6) and the second flow control valve (7) are kept in a closed position. The first direction may be defined as the flow of secondary fluid from the secondary fluid inlet port valve (4) along the secondary loop to the secondary fluid outlet port valve (5). In other words, the first direction can be defined as flow of secondary fluid from an enclosure inlet point (11) towards an enclosure outlet point (10) of the heat exchanger. Thus, during regular operation, the secondary fluid does not enter the back flushing circuit. During flush or back flush operation of the heat exchanger (1), the secondary fluid inlet port valve (4) and the secondary fluid outlet port valve (5) are kept in closed position whereas the first flow control valve (6) and the second flow control valve (7) are kept in an open position. The pressurized fluid such as water from the fire main line enters the secondary loop of the heat exchanger (1) and flows in the second direction thereby flushing the deposited silt, mud or foreign materials. Thus during flushing operation, the pressurized fluid i.e. water from the fire main line is inputted through the pressurized fluid inlet connection (8) into the secondary loop of the heat exchanger and from the secondary loop of the heat exchanger to the drain tank through the flush fluid outlet connection (9). The flushed slit, mud or foreign materials from the heat exchanger (1) are drained from the flush fluid outlet connection (9) into the drain tank via the second flow control valve (7). During the flush operation, the lubricant may continue to flow for brief time in the primary loop of the heat exchanger (1). To resume the heat exchanger (1) back to regular operation, the first flow control valve (6) and the second flow control valve (7) are first closed and then, the secondary fluid inlet port valve (4) and the secondary fluid outlet port valve (5) are opened.
[0025] In one aspect of the present invention, a method for cleaning a heat exchanger (1) is disclosed. The method comprises the steps of closing a secondary fluid inlet valve (4) and a secondary fluid outlet valve (5) for stopping flow of secondary fluid in secondary loop of the heat exchanger (1). Further, the method comprises opening a first flow control valve (6) and a second flow control valve (7) mounted on highly pressurized fluid inlet connection (8) and flush fluid outlet connection (9) respectively for controlling flow of highly pressurized fluid from a fluid source. Furthermore, the method comprises flushing highly pressurized fluid from an enclosure outlet point (10) towards an enclosure inlet point (11) for cleaning an enclosure of the heat exchanger (1) to remove deposited slit, mud or foreign material. After cleaning the enclosure of the heat exchanger (1), the first flow control valve (6) and the second flow control valve (7) mounted on the highly pressurized fluid inlet connection (8) and the flush fluid outlet connection (9) respectively are closed for stopping flow of highly pressurized fluid from a fluid source and simultaneously the secondary fluid inlet valve (4) and the secondary fluid outlet valve (5) are opened for controlling flow of secondary fluid in secondary loop of the heat exchanger (1) to resume regular operation of the heat exchanger (1).
[0026] Further, the invention can be used, but not limited to, in the following applications.
[0027] One embodiment of the invention can be used in dredgers, tugs, ships and other industrial applications.
[0028] Exemplary embodiments discussed above may provide certain advantages. Though not required to practice aspects of the disclosure, these advantages may include those provided by the following features.
[0029] Some object of the present invention enables quick flushing of the heat exchanger.
[0030] Some object of the present invention prevents stopping of the operation of the heat exchanger for cleaning purpose.
[0031] Some object of the present invention delays frequent maintenance of the heat exchanger till further scheduled major maintenance.
[0032] Some object of the present invention prevents large breakdown hours and improves productivity.

,CLAIMS:

1. A system for cleaning a heat exchanger (1) comprises:
a heat exchanger (1) configured with primary loop and a secondary loop for transfer of heat from a primary fluid circulated through a primary loop to a secondary fluid circulated through a secondary loop; and
a flushing circuit configured to flush highly pressurized fluid for cleaning the inner surface of the secondary loop and the outer surface of the primary loop in the heat exchanger (1).

2. The system as claimed in claim 1, wherein a secondary fluid inlet port valve (4) and a secondary fluid outlet port valve (5) is configured to control the flow of the secondary fluid in said secondary loop of the heat exchanger (1).

3. The system as claimed in claim 1, wherein said flushing circuit is configured with a highly pressurized fluid inlet connection (8) and a flush fluid outlet connection (9) connected to the secondary loop of the heat exchanger (1) to facilitate flushing of highly pressurized fluid from a fluid source along a second direction for cleaning the enclosure of heat exchanger (1).

4. The system as claimed in claim 3, wherein said flushing circuit is configured with a first flow control valve (6) and a second flow control valve (7) mounted on said highly pressurized fluid inlet connection (8) and flush fluid outlet connection (9) respectively to control flow of highly pressurized fluid along the second direction.

5. The system as claimed in claim 1, wherein said flushing circuit or a back flushing circuit is configured to remove deposited slit, mud or foreign material from the enclosure of the heat exchanger (1) by flushing highly pressurized fluid.

6. The system as claimed in claim 1, wherein said flow control valve (6) and flow control (7) are configured from one of a ball valve, a gate valve or a globe valve.

7. The system as claimed in claim 1, wherein said flushing circuit is configured for maintenance of the heat exchanger (1) by flushing of highly pressurized fluid in continuation with regular operation of the heat exchanger (1).

8. A method for cleaning a heat exchanger (1) comprising the steps of:
closing a secondary fluid inlet valve (4) and a secondary fluid outlet valve (5) for stopping flow of secondary fluid in secondary loop of the heat exchanger (1) and simultaneously opening a first flow control valve (6) and a second flow control valve (7) mounted on highly pressurized fluid inlet connection (8) and flush fluid outlet connection (9) respectively for controlling flow of highly pressurized fluid from a fluid source;
flushing highly pressurized fluid from an enclosure outlet point (10) towards an enclosure inlet point (11) for cleaning an enclosure of the heat exchanger (1) to remove deposited slit, mud or foreign material by; and
closing the first flow control valve (6) and the second flow control valve (7) mounted on the highly pressurized fluid inlet connection (8) and the flush fluid outlet connection (9) respectively for stopping flow of highly pressurized fluid from a fluid source and simultaneously opening the secondary fluid inlet valve (4) and the secondary fluid outlet valve (5) for controlling flow of secondary fluid in secondary loop of the heat exchanger (1) to resume regular operation of the heat exchanger (1).