Profiled Transpired Solar Collector for Low-Velocity Air Heating
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Solution Overview
Problem
Transpired solar collectors are inefficient at low approach velocities, resulting in a limited increase in air temperature due to wind sensitivity and reduced heat transfer, limiting their application to processes requiring higher temperature increases.
Innovation Solution
A transpired solar collector design featuring a profiled absorber plate and back plate with angled troughs and ridges, creating turbulence and increasing air residence time, which enhances heat transfer and temperature increase, while being cost-effective and easy to manufacture using standard metal plates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high approach velocities are used to draw air through the absorber plate, then large volumes of air pass through the perforations and efficiency is high, but the temperature increase of the outside air is relatively small
Solution Approach 1:
The absorber plate is segmented into multiple zones with different perforation densities. The first zone has a higher density of perforations to draw in large volumes of air at high approach velocities, while the second zone has a lower density to allow for longer residence time and greater temperature increase. This segmentation allows different regions of the absorber plate to perform different functions in the air heating process.
2Temperature
If lower approach velocities are used to achieve higher temperature increases, then the efficiency of transpired solar collectors rapidly decreases due to wind sensitivity
Solution Approach 1:
Different zones of the absorber plate are given different local qualities in terms of perforation density. The first zone is optimized for high velocity air intake with higher perforation density, while the second zone is optimized for heat transfer with lower perforation density. This allows the system to maintain high efficiency in the first zone while achieving high temperature increases in the second zone.
3Temperature
If much of the heating of air takes place at the outside of the absorber plate, then the heating is wind-sensitive and limits application to circumstances where limited temperature increase is acceptable
Solution Approach 1:
The invention moves the primary heating process from the external boundary layer (two-dimensional surface heating) to the internal flow path (three-dimensional volumetric heating). By drawing air through the perforations into the collector space where it passes over the absorber plate interior surface, the heating occurs in a controlled internal environment rather than being subject to external wind conditions.
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 achieves a higher temperature increase and improved heat exchange at low approach velocities, making it suitable for applications requiring higher temperature increases, such as room heating, with measured efficiency improvements and cost-effectiveness.
Implementation Method 1
an absorber plate provided with multiple perforations wherein the absorber is part of an enclosure forming an air collector space
Implementation Method 2
the profile comprises one or more troughs and ridges and wherein the longitudinal direction of the troughs and ridges of both the absorber plate and the back plate is at an angle to the general direction of the air flow in the collector space
Implementation Method 3
By providing a negative pressure in the collector space outside air is drawn through the perforations into the collector space
Data Source
Figure 1~3
Figure 4a~4c
Figure 5a~5c
AI summary
The invention relates to a transpired solar collector (1) comprising an absorber plate (2), provided with multiple perforations (3), and a back plate (4), wherein the absorber plate (2) and the back plate (4) define a collector space (5), wherein at least one of the absorber plate (2) and back plate (4) is profiled, the profile comprising one or more troughs and ridges (6, 7) and wherein the transpired solar collector (1) is designed to operate at low air approach velocities.