Subsea Heat Exchanger with Nested Pipes for Natural Convection
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Solution Overview
Problem
Subsea installations face challenges in efficiently cooling insulation and cooling fluids due to limited outer surface area for heat transfer, leading to increased temperature and pressure issues in deep water environments.
Innovation Solution
A subsea heat exchanger design featuring a first and second chamber connected by an outer pipe and inner pipe with a gap for fluid communication, allowing natural convection-driven heat transfer without pumps, and enabling scalable solutions by varying pipe number and length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If cooling is provided via the outer surface of the tank, then the structure is simple, but the cooling efficiency is insufficient due to limited surface area
Solution Approach 1:
The heat exchanger employs a nested pipe configuration where an inner pipe is surrounded by an outer pipe, creating multiple heat transfer pathways within a compact structure. This nested arrangement increases the effective heat transfer surface area without proportionally increasing the overall device volume, thereby improving cooling efficiency while maintaining structural compactness suitable for subsea installations.
Solution Approach 2:
The invention transitions from two-dimensional surface cooling (outer tank surface) to three-dimensional volumetric cooling by introducing internal heat exchanger pipes that extend into the fluid volume. The inner and outer pipes create multiple heat transfer surfaces distributed throughout the tank interior, effectively utilizing the third dimension to increase cooling capacity.
2Temperature
If additional cooling surfaces are added to the tank, then cooling efficiency improves, but the device complexity increases
Solution Approach 1:
The heat exchanger is segmented into distinct functional components: an inner pipe for one flow direction, an outer pipe for another flow direction, and connection elements linking them to the tank. This segmentation allows each component to be optimized independently and facilitates modular assembly, reducing overall system complexity while achieving enhanced cooling through multiple heat transfer surfaces.
3Volume of stationary object
If a compact heat exchanger design is used, then the fluid volume is small, but the heat transfer surface area must be maximized
Solution Approach 1:
The concentric arrangement of inner and outer pipes creates multiple heat transfer surfaces within a minimal volume envelope. The annular space between the pipes provides additional heat transfer area while occupying minimal space, effectively maximizing the heat transfer surface area to volume ratio.
Solution Approach 2:
The design utilizes three-dimensional space efficiently by creating heat transfer surfaces in multiple directions - the inner pipe provides internal surface area, the outer pipe provides external surface area, and the annular gap provides additional heat transfer pathways, thereby maximizing heat transfer surface area within compact volumetric constraints.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design provides effective heat transfer with a small fluid volume relative to the heat transfer surface, suitable for deep water environments, and can be applied to various subsea assemblies, including transformers, motors, and switchgears, without the need for pumps, enhancing cooling efficiency.
Implementation Method 1
The subsea heat exchanger can be driven by natural convection without any pumps
Implementation Method 2
The insulation and/or cooling fluid is often cooled via the outer surface of the tank to the surrounding sea water
Implementation Method 3
providing a heat transfer surface to the surrounding fluid
Data Source
Figure 1~2
Figure 3~4
AI summary
The invention relates to a subsea heat exchanger (1) comprising a first (2) and a second (3) chamber, the first chamber (2) comprising a fluid inlet (4) and the second chamber (3) comprising a fluid outlet (5), wherein the first chamber (2) and the second chamber (3) are connected with at least one outer pipe (6). The heat exchanger (1) comprises an inner pipe (7) surrounded by the outer pipe (6). A first end (8) of the inner pipe (7) extends into the first chamber (2) and is connected to a first connection point (9a) in the first chamber (2), a second end (10) of the inner pipe (7) extends into the second chamber (3) and is connected to a second connecting point (9b) in the second chamber (3). Between the outer pipe (6) and the inner pipe (7) is a gap (12) open to the first (2) and the second chamber (3) providing a fluid communication between the first chamber (2) and the second chamber (3). The first (8) and the second ends (10) of the inner pipe (7) are open providing a flow path for surrounding fluid (13) through the inner pipe (7).The invention relates also to a subsea assembly comprising the subsea heat exchanger (1) and to a use of a subsea heat exchanger (1).