This invention relates to a solar fluid heater featuring a double-walled evacuated glass tube with an inner absorber tube and an outer protective tube. A working fluid flow tube runs through the absorber tube, allowing fluid to enter through the annular space and exit through the inner tube. A turbulator is placed between the absorber and flow tube to enhance heat transfer. This design ensures efficient fluid heating and is well-suited for industrial thermal applications.
Figure 1. Evacuated Glass Tube Solar Air Heater (Fixed Parabolic Reflector: Cost INR 7,500 to 9,000/m2, Weight 5 to 7 kg/m2, App 2.1 m2 Air In 29°C, Air Out 150°C to 300°C, Heat Duty 0.3 to 0.375 kW/m2, Air Flow 100 lpm/m2, Efficiency 40% to 60% based on Global Radiation Isolation 0.75 to 1.2 kW/m2, CR 2.1)
The invention addresses the need for a high-efficiency solar fluid heater capable of operating at high extraction temperatures with a low concentration ratio. It aims to deliver a lightweight, cost-effective solution that is simple to install, easy to maintain, and durable, without requiring tracking mechanisms or metal-to-glass seals.
- High Heat Transfer Efficiency: The turbulator, its open structured construction and reflector provides increased surface area of contact and surface density between the absorber tube and working fluid which increases heat transfer coefficient and ensures moderate concentration ratio.
- Compact and Lightweight: The turbulator has sufficient structural rigidity and stability but is flexible and ideal for coiled or serpentine or bent configuration of solar heater and it is located within the evacuated tube ensures its compactness. It is also flexible and lightweight.
- Increased Flow Rate: The higher thermal input raises fluid temperature and drives increased circulation through natural or forced convection.
- Low Cost and Easy Deployment: It has simple construction with fewer moving parts; no tracking mechanism needed with no need for periodic re-evacuation.
The solar fluid heater features an evacuated double-walled glass tube consisting of an inner absorber tube and an outer protective tube, spaced apart with the space evacuated. A working fluid flow tube is placed inside the absorber tube, positioned near the closed end and extending outward at the open end. A turbulator, made of a flexible wiry helical structure of thermally conductive wire windings held by a springy material wire, is located between the absorber tube and the working fluid tube to enhance heat transfer. The working fluid flows through the space between the absorber and flow tube (inflow) and within the working fluid tube itself (outflow). Materials for the tubes and turbulator wires include copper, aluminium, phosphor bronze, mild steel, stainless steel, or alloys. The outer surfaces of the protective and absorber tubes may be coated with anti- reflective or absorbent films to improve efficiency. Additionally, some designs include a parabolic reflector made from flexible aluminium or plastic-coated reflective sheets positioned around the evacuated tube to focus solar energy. Fixed Parabolic Reflector is shown in picture: Cost INR 7,500 to 9,000/m2, Weight 5 to 7 kg/m2, App 2.1 m2. Air In 29°C, Air Out 150°C to 300°C, Heat Duty 0.3 to 0.375 kW/m2, Air Flow 100 lpm/m2, Efficiency 40% to 60% based on Global Radiation Isolation 0.75 to 1.2 kW/m2, CR 2.1.
Technology has been extensively tested in the HPLIITB for over a year, while once-through heating of ambient air in the range of 150°C to 300°C. Technology can be demonstrated at the module level for a specific application and transferred for commercialisation for heating air up to 300°C.
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This solar fluid heater promotes sustainable energy use by harnessing solar power for thermal applications, reducing dependence on fossil fuels and lowering carbon emissions. Its low cost, easy installation, and high efficiency make it ideal for rural and urban deployment, supporting energy access, economic development, and environmental conservation.
- Renewable energy
- Industrial process heating
- Agriculture (drying, greenhouse heating)
- Food and beverage processing
- Chemical & Pharmaceutical industries
- Hospitality (hot water systems)
- District heating systems
- Building and construction (HVAC integration)
Geography of IP
Type of IP
2502/MUM/2010
374949