Radiation absorbing metal pipe

Abstract

The invention relates to the field of solar energy usage and, particularly, to solar systems, which operate on the base of concentration of direct solar radiation. The invention proposes a radiation absorbing metal pipe intended for heating gaseous medium or gaseous-liquid mixture.The proposed radiation absorbing metal pipe is constructed from perforated plates. These plates are provided with inclined or two-stage upright rims. The plates are stacked and sealingly joined with formation of a tubular unit.Such tubular units with absorbing coatings of their external surfaces can be applied in following solar thermal systems: parabolic trough collectors; solar thermal collectors with usage of linear Fresnel reflectors; for a system with an array of tracking mirrors and a central receiver mounted on a tower or on the ground.

Description

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH[0001]Not applicableFIELD OF THE INVENTION[0002]This invention relates to a field of solar energy usage and, particularly, to solar systems, which operate on the base of concentration of direct solar radiation. In addition, the invention can be used for superheating steam in thermal power plants.BACKGROUND OF THE INVENTION[0003]This invention relates to a field of solar energy usage and, particularly, to solar systems, which operate on the base of concentration of direct solar radiation.[0004]The solar systems may be used as a source of thermal energy in power plants, or as a source of thermal energy for carrying out thermo-chemical processes.[0005]There are three main types of the solar concentrating systems, which may put into practice the proposed invention:1. Parabolic trough collectors (PTCs);2. Solar thermal collectors with application of linear Fresnel reflectors (LFRs).3. An array of flat or slightly concave mirrors, or heliost...

AI Technical Summary

Benefits of technology

This patent describes a new method for improving heat transfer in solar radiation absorbing tubes used in solar concentrating systems. The method involves adding a layer of metal perforations to the internal surface of the tube and creating a multi-jet flow between these fins. This results in a higher value of the heat transfer coefficient, which is important for efficient heat transfer. The patent also describes the use of a selective absorptive coating on the outer surface of the tube to enhance heat transfer. The invention can be applied to both tracking trough parabolic mirrors and tracking one-curved Fresnel mirrors. The patent also describes the construction of a solar radiation receiving chamber with a radiation receiving pipe made of stacked metal perforated plates.

Problems solved by technology

There are two technical problems in operation of the receivers of the PTC, LFR and STP systems.

Uneven heating of radiation absorbing pipes in their circumferential direction by concentrated radiation and, as result, their deformation.

This deformation is expressed in bending the radiation absorbing pipes out of their position in the focal areas and diminishment of their efficiency.

In addition, it can cause mechanical failure of the receiver, especially, for PTC and LFR systems.

An additional technical problem for PTC, LFR and STP systems is relatively low values of heat transfer coefficients for gaseous heat transfer medium flowing in the radiation absorbing pipes.

This causes elevation of heat losses mainly by thermal radiation and, in turn, diminishes additionally efficiency of PTC, LFR and STP systems, when they are used for superheating steam, heating the pressurized air or heating a gaseous medium for execution of thermo-chemical reactions.

However, the longitudinal heat transfer fins cannot enhance the internal surface of the radiation absorbing pipe in fife-to-one ratio or more and, at the same time, to increase significantly the heat transfer coefficient for the fins themselves as for pin-wise fins.

It is clear, that this technical solution does not solve the problem of low values of the heat transfer coefficient for heat transfer from the internal surface of the steam generator tube, when the generated saturated steam to be superheated.

This patent does not solve the problem of enhancing heat transfer for the internal surface of the guide tube.

We see that this patent application does not solve the problem of steam superheating.

The proposed rifled internal surface of the tubes does not provide a required enhancement of the heat transfer coefficient for steam superheating.

This patent application does not give any technical solution for enhancement of the heat transfer coefficient in the steam superheating unit.

We see that this patent application does not give any technical solution for enhancement of the heat transfer coefficient in the steam superheating unit.

These patent applications do not give any technical solution for enhancement of the heat transfer in the steam superheating unit.

However, these patents and patent applications describe heat exchangers intended to cool oil by a cooling liquid and they do not suitable for heating a gaseous medium by concentrated solar radiation.

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