Waste Heat Recovery Using Heat Exchanger and Heat Pump Staging
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Solution Overview
Problem
Existing methods for recovering heat from waste streams to liquid streams are inefficient, particularly when the waste stream has a higher flow rate, as they either require external energy or struggle with viscous and heterogeneous waste streams due to direct contact with heat pump evaporators.
Innovation Solution
A method combining a heat exchanger and a heat pump, where the waste stream is divided into two parts, with the first part preheating the liquid stream using an indirect heat exchanger and the second part further heating it using a closed liquid circuit heat pump, avoiding direct contact with the evaporator and optimizing efficiency by selecting flow rates to maximize heat transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a heat exchanger is used to transfer heat from waste stream to liquid stream, then heat transfer occurs naturally without additional energy, but the liquid stream cannot be heated to a temperature higher than that of the waste stream
Solution Approach 1:
The waste stream is divided into two separate streams: a first stream passes through a heat exchanger to preheat the liquid stream, while a second stream passes through a heat pump to provide additional heating. This segmentation allows each component to operate optimally within its temperature range, with the heat pump boosting the liquid stream temperature beyond what the waste stream alone can provide.
Solution Approach 2:
The system merges two heat recovery approaches (heat exchanger and heat pump) into a single integrated system. The heat exchanger handles the bulk heat transfer naturally, while the heat pump supplements it to achieve higher temperatures, combining the advantages of both methods without requiring external energy sources.
2Temperature
If a heat pump is used to transfer heat from waste stream to liquid stream, then heat can be transferred efficiently even with small temperature difference, but external energy must be supplied to drive the compressor
Solution Approach 1:
The heat exchanger performs preliminary heating of the liquid stream using the waste stream before the heat pump processes it further. This preheating reduces the temperature lift required by the heat pump, improving its efficiency and reducing the external energy needed to drive the compressor.
3Quantity of substance
If the waste stream has a relatively high flow rate compared with the stream to be heated, then more heat is available, but only a fraction of the heat from the waste stream can be recovered
Solution Approach 1:
The system ensures continuous heat recovery by processing both the first and second streams of the waste stream through different mechanisms. The heat exchanger continuously extracts heat from the first stream, while the heat pump continuously extracts heat from the second stream, maximizing the utilization of available heat from the high-flow waste stream without interruption or loss.
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
This approach enhances heat recovery efficiency by allowing the heat pump to utilize the residual heat from the waste stream, achieving higher temperatures in the liquid stream while maintaining ease of maintenance and avoiding the need for external energy, especially effective for high-flow waste streams.
Implementation Method 1
Heat exchangers have the advantage that the heat transfer occurs naturally, and avoid that additional energy has to be brought into the system for the stream to be heated. A certain amount of heat will be transferred through natural conduction from the stream with the highest temperature to the stream with lowest temperature
Implementation Method 2
A heat pump includes a closed circuit in which a refrigerant is sent sequentially through a compressor, a condenser, a throttle valve and an evaporator. The refrigerant evaporates, compresses, condenses and expands in the closed cycle and transfers in this way heat from the evaporator to the condenser.
Implementation Method 3
The refrigerant evaporates, compresses, condenses and expands in the closed cycle and transfers in this way heat from the evaporator to the condenser
Data Source
AI summary
The present invention relates to a method to add heat from a waste stream (1) to a liquid stream (2) wherein the liquid stream is first thermally pre-treated by adding a first part of the heat of the waste stream (1) to the liquid stream (2) by means of a heat exchanger (3) and next heat is added to the pre-treated liquid stream (2) by means of a heat pump (4), characterized in that the heat which is released to the liquid stream (2) by means of the heat pump (4) is substantially derived from the second part of the heat of tie waste stream (1) and an installation (10) therefore.