Desalinating drip-irrigation system

• US 4,698,135 A
• Filed: 10/03/1985
• Issued: 10/06/1987
• Est. Priority Date: 02/10/1983
• Status: Expired due to Fees

• Current Assignee: Sirdan Research Limited
• Original Assignee: Sirdan Research Limited
• Inventors: Raab, Simon
• Primary Examiner(s): Bashore, S. Leon
• Assistant Examiner(s): Manoharan, V.
• Application Number:
  US06/783,332
• Time in Patent Office: 733 Days
• Field of Search: 202/188, 202/187, 202/237, 202/234, 203/DIG. 1, 203/10, 203/DIG. 17, 159/903, 159/DIG. 28, 159/DIG. 27, 159/DIG. 23, 47/48.5, 47/79
• US Class Current: 202/234
• CPC Class Codes: A01G 25/00 Watering gardens, fields, sports grounds or the like special apparatus or adaptations for fertilising-liquids A01C23/00; nozzles or outlets, spraying apparatus B05B
• CPC Class Codes: B01D 61/362 Pervaporation
• CPC Class Codes: B01D 71/36 Polytetrafluoroethene
• CPC Class Codes: C02F 1/14 using solar energy
• CPC Class Codes: Y02A 20/124 Water desalination
• CPC Class Codes: Y02A 20/142 Solar thermal; Photovoltaics
• CPC Class Codes: Y02A 20/212 Solar-powered wastewater sewage treatment, e.g. spray evaporation
• CPC Class Codes: Y02A 40/22 Improving land use; Improving water use or availability; Controlling erosion
• CPC Class Codes: Y10S 159/27 Micropores
• CPC Class Codes: Y10S 159/28 Porous member
• CPC Class Codes: Y10S 159/903 Solar
• CPC Class Codes: Y10S 203/01 Solar still
• CPC Class Codes: Y10S 203/18 Control

Abstract

A system is provided for use adjacent a plant supporting material to be irrigated, for converting salt water into fresh water and dispensing the fresh water dripwise to the plant supporting material. The system comprises an evaporator member made of microporous hydrophobic material and having first and second surfaces, the microporous hydrophobic material permitting water vapor to diffuse through the member between the first and second surfaces thereof while preventing liquid water from passing therethrough, and a condenser including a condensing surface is spaced from the second surface of the evaporator member to define a gap therebetween. The condensing surface is in liquid flow communication with the plant supporting material to be irrigated. A conduit is provided for conducting a flow of salt water along the first surface of the evaporator members.

Claims

1. A desalinating drip-irrigation system for use adjacent a plant supporting material to be irrigated, for converting salt water into fresh water and dispensing said fresh water dripwise to said plant supporting material, said system comprising:

an evaporator member consisting of a microporous hydrophobic material and having first and second surfaces, said microporous hydrophobic material permitting water vapor to diffuse through said member between said first and second surfaces thereof while preventing liquid water from passing therethrough;

a condenser member having a condensing surface spaced from said second surface of said evaporator member to define a gap therebetween, said condensing surface being in liquid flow communication with said plant supporting material to be irrigated;

means for conducting a flow of salt water along said first surface of said evaporator member; and

means for generating a temperature gradient between said first surface of said evaporator member and said condensing surface, said temperature gradient generating means including an evaporator cooling member forming with said condenser member a cooling chamber for containing a cooling liquid, said evaporator cooling member consisting of said microporous hydrophobic material and causing evaporative cooling of said liquid on exposure of said evaporator cooling member to dry ambient air, thereby cooling said condensing surface and generating a temperature gradient which causes evaporation of said salt water at said first surface and diffusion of the resulting water vapor through said evaporator member from said first surface to said second surface thereof and across said gap so as to condense on said condensing surface and to thereby form condensed fresh water which is allowed to drip off said condensing surface to be absorbed by said plant supporting material.

2. A desalinating drip-irrigation system as claimed in claim 1, wherein said microporous hydrophobic material is microporous polyethylene.

3. A desalinating drip-irrigation system as claimed in claim 1, wherein said microporous hydrophobic material is selected from the group consisting of microporous, expanded polytetrafluoroethylene and polypropylene.

4. A desalinating drip-irrigation system as claimed in claim 1, wherein said microporous hydrophobic material has pores with a size of about 0.01 to about 0.2μ

.

5. A desalinating drip-irrigation system as claimed in claim 1, wherein said evaporator cooling member is a hollow evaporator cooling tube supported by said plant supporting material, said evaporator cooling tube having an inner surface and an outer surface exposable to said dry ambient air;

said condenser member is a hollow condenser tube arranged coaxially within said evaporator cooling tube and formed with a plurality of spaced-apart outwardly extending protrusions disposed circumferentially about said condenser tube and each having an apex engaging said inner surface of said evaporator cooling tube for supporting said condenser tube within said evaporator cooling tube, said condenser tube having an inner surface face constituting said condensing surface and an outer surface spaced from said inner surface of said evaporator cooling tube with said cooling chamber defined therebetween, each said protrusion having at the apex thereof drip-holes extending through said evaporator cooling tube for providing said liquid flow communication between said inner surface of said condenser tube and said plant supporting material; and

wherein said evaporator member is a hollow evaporator tube having inner and outer surfaces constituting respectively said first and second surfaces and also defining an inner channel constituting said salt water conducting means, said evaporator tube being arranged coaxially within said condenser tube and formed with a plurality of spaced-apart outwardly extending protrusions disposed circumferentially about said evaporator tube and each having an apex engaging said inner surface of said condenser tube intermediate said protrusions of said condenser tube for supporting said evaporator tube within said condenser tube, each protrusion of said evaporator tube having at the apex thereof openings extending through said condenser tube for providing a feed of salt water from said channel of said evaporator tube to said cooling chamber, whereby exposure of said outer surface of said evaporator cooling tube to said dry ambient air causes evaporative cooling of the salt water contained in said cooling chamber, thereby cooling said inner surface of said condenser tube and generating said temperature gradient.

6. A desalinating drip-irrigation system as claimed in claim 1, wherein said evaporator cooling member is an evaporator cooling plate constituting a first sidewall of a housing having a second sidewall opposite said first sidewall with top and bottom walls interconnecting said first and second sidewalls, each of said sidewalls having inner and outer surfaces and said bottom wall being supported by said plant supporting material to be irrigated;

said evaporator member is an evaporator plate arranged within said housing and upstanding from said bottom wall thereof, said evaporator plate having parallel opposed surfaces constituting said first and second surfaces with said first surface spaced from said inner surface of said second sidewall to define a salt water channel therebetween, said channel constituting said salt water conducting means;

said condenser member is a condenser plate arranged within said housing intermediate said evaporator plate and said first sidewall and upstanding from said bottom wall, said condenser plate having parallel opposed surfaces, one of which constitutes said condensing surface and the other is spaced from said inner surface of said first sidewall with said cooling chamber formed therebetween; and

wherein said bottom wall is provided with drip-holes disposed between said evaporator plate and said condenser plate for providing said liquid flow communication between said condensing surface of said condenser plate and said plant supporting material, and said evaporator cooling plate constituting said first sidewall has an outer surface exposable to said dry ambient air, whereby exposure of said outer surface of said evaporator cooling plate to said dry ambient air causes evaporative cooling of said liquid contained in said cooling chamber, thereby cooling said condensing surface of said condenser plate and generating said temperature gradient.

7. A desalinating drip-irrigation system as claimed in claim 6, wherein said second sidewall is made of solar radiation absorbent material and has an outer surface exposable to solar radiation and wherein said salt water channel is in liquid flow communication with said cooling chamber for providing a feed of salt water thereto and subjecting same to evaporative cooling, whereby solar radiation impinging upon said outer surface of said second sidewall with said outer surface of said evaporator cooling plate exposed to said dry ambient air causes said salt water contained in said channel to increase in temperature, thereby increasing said temperature gradient.

8. A desalinating drip-irrigation system as claimed in claim 7, wherein said outer surface of said second sidewall is black for maximum retention of solar energy.