Horizontal Extraction and Return Extensions in liquid storage tanks

Abstract

This invention is an improvement to the shape of liquid storage tanks, in particular to unpressurized molded polymer tanks used for thermal storage in solar systems. All aspects of this invention are well suited to solar storage tanks, and individual aspects are suited to other liquid tank applications.This invention provides a formed horizontal extension at the bottom of the tank. From the top of this lower extension, a hollow vertical stub provides a reliable connection to a circulator pump. Thermal performance is enhanced by ensuring the lowest and coolest water is delivered to the array of rooftop solar collectors without entraining debris from the bottom of the tank.At the top of the tank, a similar horizontal extension is used to distribute hot water returning from the solar collectors. Flow velocity is eliminated and a curving lower edge allows return water to find the matching thermocline to avoid de-stratifying.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application does not cross-reference existing non-provisional utility patent applications. However, it is related to USPTO provisional application 61 / 404,934.STATEMENT REGARDING STATE OF CALIFORNIA SPONSORED RESEARCH OR DEVELOPMENT[0002]This invention was made with State of California support under California Energy Commission grant number PIR-08-012. The Energy Commission has certain rights to this invention.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT[0003]Not applicable.REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING COMPACT DISC APPENDIX[0004]Not applicable.BACKGROUND OF THE INVENTION[0005]There are three methods commonly used in the production of liquid storage tanks. Steel and stainless steel tanks are fabricated from sheet material that is cut and welded, either automated or by hand. Their resistance to elevated pressures and temperatures makes them popular for domestic water heaters an...

AI Technical Summary

Benefits of technology

[0016]When applied to various basic tank shapes, this invention provides a formed horizontal extension at the bottom of the tank. From this lower horizontal extension, a stub is directed upwardly to provide a secure and easily-maintained connection to a circulator pump. Because the stub is oriented vertically, the structural load of the pump is well transmitted to the tank with minimal stresses within the tank material.

[0017]At the top of the tank, a similar horizontal extension is used to distribute hot water returning from the array of rooftop solar collectors (or some other heating process such as a boiler). This extension acts like a baffle to reduce or eliminate the flow velocity and enhance thermal stratification within the tank. A curving lower edge to the upper horizontal extension allows return water to find the thermocline with matching temperature. This allows useful heat to be added to the storage tank without disrupting stratification even if the return water is cooler than the water at the top of the tank.

[0018]The ideal embodiment of this invention incorporates both lower and upper horizontal extensions. Used in a solar thermal system, the upper horizontal extension would include a cylindrical through passage to support a riser pipe mounted to the discharge side of the pump. This places both connections together at the top of the tank for convenient connection to the collector array, and also makes it easy to deliver tanks to the site with pumps pre-installed at the factory. With careful design of the tank, the pump can be contained entirely within the footprint of the tank.OBJECTS OF THE INVENTION

[0019]1. To provide the lowest possible horizontal exterior tank surface from which an upward, vertically-directed flow stream can enter the circulator pump after being drawn slowly and horizontally from the lowest level of the tank without entraining any debris that may have settled out of solution and collected on the tank bottom.

[0020]2. To form a molded tank that maximizes stratification in solar heating applications by incorporating extensions designed to slow and disburse liquid flow streams leaving and entering the tank.

[0021]3. To provide the highest possible horizontal exterior tank surface from which a downward, vertically-directed flow stream can enter the tank slowly and horizontally at the highest level of the tank, and entering along an outer tank wall, allowing, the slow-moving return liquid to ooze downward toward its own temperature level when return liquid is cooler than tank-top liquid.

Problems solved by technology

But rising material costs and fabrication expense result in high prices on a storage volume basis.

For these reasons and also high dry tank weights, larger liquid storage tanks are usually unpressurized.

However, there is no practical limitation preventing the incorporation of this invention into fabricated steel vessels or tanks employing a flexible liner.

For applications where a pump is used to move liquid from the tank through a circuit, the weight and vibration of the pump (usually cantilevered) result in frequent leaks at the penetration.

Such a tank may or may not be designed to take advantage of stratified thermal storage.

But typical, piping flow velocities of 1 m / sec or more cause mixing that damages stratification, and the impact is particularly damaging when there are vertical components to the return velocity.

Images