Evaporative Air Conditioning Handbook

467 Pages·1986·35.127 MB·English

by  Dr. John R. Watt (auth.)

EVAPORATIVE AIR CONDITIONING
HANDBOOK
EVAPORATIVE AIR
CONDITIONING HANDBOOK
Second Edition
Dr. John R. Watt
with the assistance of
Richard L. Koral
Loren W. Crow
Alfred Greenberg
KAPARCHIEF
CHAPMAN & HALL
New York London
First published 1986
by Chapman and Hall
29 West 35 Street, New York, N.Y. 10001
Published in Great Britain by
Chapman and Hall Ltd
II New Fetter Lane, London EC4P 4EE
© 1986 Chapman and Hall
All Rights Reserved. No part of this book may be
reprinted, or reproduced or utilized in any form
or by any electronic, mechanical or other means,
not known or hereafter invented, including
photocopying and recording, or in any information
storage or retrieval system, without permission in
writing from the publishers.
Library of Congress Cataloging-in-Publication Data
Watt, John R.
Evaporative air conditioning handbook.
Rev. ed. of: Evaporative air conditioning. 1st ed.
1963.
Bibliography: p.
Includes index.
\. Air conditioning. I. Watt, John R. Evaporative
air conditioning. 1963. II. Title.
TH7687.W3 1986 697.9 86-17172
ISBN-13 :978-1-4612-9387-3 e-ISBN-13:978-1-4613-2259-7
DOLlO.IO07/978-1-4613-2259-7
PREFACE TO THE 1963 EDITION
Air conditioning boosts man's efficiency no less than his comfort. Air-conditioned
homes, offices, and factories unmistakably raise human productivity and reduce
absenteeism, turnover, mistakes, accidents and grievances, especially in summer.
Accordingly, many employers every year cool workrooms and offices to raise summer
profits. Employees in turn find cool homes enhancing not only comfort and prestige
but also personal efficiency and income.
With such economic impetus, low-cost summer cooling must irresistibly spread to
all kinds of occupied buildings.
Refrigeration provides our best cooling, serving well where people are closely
spaced in well-constructed, shaded, and insulated structures. However, its first and
operating costs bar it from our hottest commercial, industrial, and residential
buildings.
Fortunately, evaporative cooling is an economical substitute in many regions. First
used in Southwest homes and businesses and in textile mills, it soon invaded other
fields and climates. In 1946, six firms produced 200,000 evaporative coolers; in 1958,
25 firms produced 1,250,000, despite the phenomenal sale of refrigerating window air
conditioners.
Though clearly secondary to refrigeration, evaporative cooling is 60 to 80 percent
cheaper to buy and operate. Thus, it is economical for moderate income groups and
climates where summers are short. Moreover, it cheaply cools hot, thinly constructed
mills, factories, workshops, foundries, powerhouses, farm buildings, canneries, etc.,
where refrigerated cooling is prohibitively expensive.
However, because evaporative cooling is the product of small regional companies,
it is little known nationally. As our second-best form of comfort cooling and as the
only cooling economical for many industrial plants, it deserves wider understanding.
This book attempts to supply it.
PREFACE TO THE 1986 EDITION
In the 23 years following the original edition, evaporative cooling sales suffered
badly as refrigerative air conditioning became inexpensive enough to displace it. The
latter provided greater comfort and independence from weather conditions, quieter
and less drafty cooling, and easier incorporation into most heating systems. Its
installations also were often more sightly.
Evaporative cooling. declined most in rich and prestige-conscious Southern
California, where refrigerative cooling better excluded regional smog. Several manu
facturers and hundreds of dealers left the field.
However, arid and less prosperous Arizona, Nevada, New Mexico, Colorado,
Texas, and Utah maintained steady markets where manufacturers and dealers survived
v
vi / Preface
the incursions of refrigerative cooling. The markets were saved by the area's massive
population growth and oppressive heat, which forces almost everyone to purchase
cooling.
Meanwhile, little decline occurred in the use of large evaporative cooling. The
increasing need to promote worker productivity by cooling large industrial buildings
helped sell big, versatile, spray-type air washers that could evaporatively cool when the
weather permitted, refrigeratively cool when it did not, and also heat, ventilate, and
control humidity. Because of their flexibility they spread nationwide into thousands of
factories, mills, processing and atomic and chemical plants as far outside historic
evaporative-cooling areas as Detroit itself.
Such fields as smelting, metalworking, food processing, dry-cleaning, laundering,
and power generating needed simple cooling with massive ventilation. Smaller
evaporative cooling units, using pads wet by sprays or "water slingers," met their
needs.
Then, revolutionary Munters rigid·.pad_m edia appeared. Made of mUltiple strong,
corrugated cellulose or glass-fiber sheets cemented together, they were long-lasting,
self-cleaning, and highly effective. They made possible big, simple, troublefree coolers
that replaced many air washers.
In 1973, precipitous increases in energy costs began. These handicapped refrigera
tive cooling far more than they did evaporative. Accordingly, evaporative cooling is
enjoying a vigorous comeback. New small manufacturers are appearing; established
producers and dealers are expanding. Insiders estimate that the 1973-80 growth
exceeded to percent per year; many expect sales of small coolers to grow 30 percent
yearly in the 1980s. The sale of rigid-media devices is nearly explosive.
Similarly boosted, indirect evaporative coolers, which cool air without wetting it,
are spreading widely as precoolers for ordinary evaporative or refrigerative cooling. So
combined, they cut operating costs immensely and provide cooling that serves well in
areas of moderate humidity. That promises to spread evaporative cooling into many
new regions.
Evaporative cooling today is also helping save refrigerative power costs. Millions of
tons of small- and medium-sized air conditioning and commercial refrigeration have
air-cooled condensers with low hot-weather efficiency. Many now boost summer
economy with devices that evaporatively precool outdoor air entering those condensers.
Even so, rising power costs ahead may well sideline many refrigerative window units
and small central systems.
If so, direct evaporative cooling must assume orphan cooling loads in the drier
regions, indirect evaporative cooling following suit in damper climates, staged with
direct evaporative cooling or small-scale refrigeration.
Admittedly, refrigeration usually produces better all-around comfort. However, in
its growing climatic ranges, evaporative cooling enjoys strong monetary advantages:
• Much lower equipment and installation costs
• Much lower operating and power costs
• Much lower maintenance costs
• Much greater ventilating effect, if needed
• Better air distribution without ducts
• Usually lower outdoor noise levels
In today's world of climbing energy, material and labor expense, cost advantages
seem likely to dominate 'many cooling markets for years to come. So evaporative
cooling has a rosy future.
Preface I vii
Looking Ahead
The market for evaporative cooling is enormous and growing, boosted by new
housing construction and ever-climbing power costs. According to the Census
Bureau's "Characteristics of New Housing: 1982," 66 percent of new housing starts
that year included air conditioning, a percentage that has increased yearly since 1977.
That suggests Americans increasingly consider cooling a necessity. With about
1,730,000 new housing starts in 1985, new homes with cooling approached 1,300,000.
With interest rates falling significantly that year, counting replacements and
retrofits in existing homes, cooling sales could quadruple in the next decade. Besides
these sales will be those of very large systems to commercial and industrial markets.
In spite of collapsing oil prices after 1984, power costs continue to rise. Not only do
power companies burn less oil than natural gas and coal, but also many are amortizing
inordinate outlays for atomic plants, including abandoned ones. Moreover, most
completed atomic plants operate more expensively and have more frequent shutdowns
than conventional plants. Each one completed also increases the company capital-base
against which legally allowable charges are levied.
Upward pricing is inevitable for another reason; growing summer cooling loads are
unbalancing yearly power demands, forcing utilities to expand their plants at
increasing material, labor, and equipment costs, although excess capacity exists during
the other seasons.
Because of rising power costs, population movements to the sunny states, and the
growing geographical mobility of staged indirect evaporative systems, the market share
of evaporative cooling is growing steadily and should continue to do so in the
foreseeable future. As the staged equipment becomes better known, better packaged
(Arvin Industries leads the way here), and mass-produced, its sales should mushroom,
replacing much whole-system refrigeration in many climatic regions and fields.
Solarized equipment may make a significant contribution. The September-October
1984 issue of Solar Engineering and Contracting listed firms already offering solarized
equipment. Three manufactured indirect or staged evaporative coolers, two made
photovoltaic powered direct coolers, and one offered similar evaporative precoolers for
refrigeration condensers.
The anticipated rise in solar-cell cost-efficiency will encourage such firms in the
same way that 40 percent federal income tax credits and some state tax credits did
through 1985, by subsidizing the solar components in products. Though lapsed, such
tax credits generally favored low-cost over high-cost combined installations and thus
favored evaporative over refrigerative equipment. If there are future versions of such
tax credits, they will likely be similar.
Tosummarize, strong economic trends encourage the spread of cooling to improve
human productivity and comfort. Ample reason exists for such cooling to be as
economical as possible, in both power consumption and life cycle. Evaporative cooling
seemingly leads all competitors in both respects.
John R. Watt
Atlanta, Ga.
June, 1986
TABLE OF CONTENTS
PREFACE ............................................... v
Man's Need for Cooling, Evaporative Cooling Origins, Its Early
Southwest Boom and Uses, Temporary Decline, Recent Revival, New
Types and Purposes, Economic Advantages Today, Growing Markets
Ahead, Solar Connections.
I. INTRODUCTION ......................................... 01
Evaporative Cooling Types, Long Scientific Neglect, Aid to Industrial
Productivity, Coming Triumphs, Omissions, Abbreviations, Metric
Equivalents.
II. HISTORY OF EVAPORATIVE COOLING .................. 05
Primitive Evaporative Cooling, Modern Evaporative Cooling, Eastern
Types and History, Western Types and Development, Typical Indirect
System Cooling Towers, An Early Plate-Type Indirect Cooler, Early
Drip Coolers, Mass Production Begins, Historical Importance, The
Industry Consolidates, Industry Achievements, Review Questions.
III. THEORY OF DIRECT EVAPORATIVE COOLING .......... 12
Heat and Mass Transfer, Sensible and Latent Heat, Adiabatic
Saturation, Limits of Direct Evaporative Cooling, Humidity
Measurement, Dry-Bulb and Wet-Bulb Temperatures, Psychrometric
Charts, Other Psychrometric Properties, Psychrometric Processes,
Ideal Evaporative Cooling, Ordinary Evaporative Cooling, Saturating
Efficiency, Evaporative Cooling Process in Rooms, Washed-Air
Discharge Outdoors, Indoor Relative Humidity, Review Questions.
IV. COMFORT ASPECTS OF AIR CONDITIONING ........... 26
The Organic Thermodynamics of Comfort, Heat Dissipated by
People, The Body's Means of Heat Dissipation, Bodily Governing
Factors, Organic Temperature Controls and Limits, Architectural and
Psychological Factors, The Effect of Building Size and Mass upon
Indoor Comfort, Effective Temperatures and Comfort Zones, Comfort
Charts, Limited Pertinence, Comfort Chart Adaption to Other
Conditions, An Evaporative Cooling Comfort Zone, A Proposed
Evaporative Cooling Comfort Chart, Nomograph for Rapid
Calculating of Evaporative Cooling Results, Recommended Summer
Indoor Conditions, Adjustment for Radiant Heat, Permissible
Relative Humidities, Permissible Air Motion with Evaporative
Cooling, Fresh Air Requirements, Air Cleaning, Review Questions.
ix
x / Table of Contents
V. GEOGRAPHIC RANGE AND EVAPORATIVE COOLING .. 43
Other Factors Than Humidity, Traditional Design Temperatures,
Coincident Dry- and Wet-Bulb Temperatures, Use of Diurnal
Temperature Swings, U.S. Evaporative Cooling Coincident Design
Temperatures, Selected Canadian Cooling Coincident Design
Temperatures, Climatic Considerations and the Need for Cooling,
International Comparative Weather Data, International Direct
Evaporative Cooling Applicability, Achieving Comfort, Process Path
Vectors, Wet-Bulb Temperatures that Permit Vectors to Achieve
Comfort Zones, Indirect Coolers and Geographic Range, Review
Questions.
VI. DRIP-TYPE DIRECT EVAPORATIVE COOLERS ........... 90
Cabinet Design, Fans and Motors, Motor Ratings, Pad-Holders, Pad
Materials, Water Distribution Systems, Recirculating Pumps, Pad
Thickness and Density, Air Velocity in Pads, Water Flow in Pads,
Review Questions.
VII. DRIP COOLER PROGRESS ............................. 107
Pad Sagging, Pad Clogging, Pad Scaling, Bleed-Off and Blow-Down,
Chemical Water Treatment, Pad Deterioration, Odor Problems,
Corrosion Resistance, Galvanized Steel Coolers, Stainless Steel
Coolers, Pressure Molded Plastic Coolers, Another Molded Plastic
Cooler, Fiber Glass Coolers, Composite Australian Coolers,
Exaggerated U.S. Performance Data, Controls, Idealized Drip Cooler
Controls, Solar Connections, Solar Drip Coolers, Solar Tax Credits,
Review Questions.
VIII. OTHER SMALL EVAPORATIVE COOLERS .............. 131
Portable Drip Coolers, Spot Coolers, Exhaust-Type Window-Pad
Coolers, The New Roller Pad Coolers, Automobile Evaporative
Coolers, Modern Vehicular Coolers, The Fog Chamber Coolers, A
New Small Rotary Drum Cooler, Outdoor Fog-Type Cooling, Small
Rigid-Media Coolers, Solar-Powered Small Coolers, The Future,
Review Questions.
IX. COMMERCIAL DIRECT EVAPORATIVE COOLERS ...... 146
Slinger-Type Coolers, Adaptability, The Saturation Pads or "Filters,"
Pad Wetting Devices and Problems, Pump-and-Nozzle Pad Spraying,
Air-Cleaning Effect, The Proper Name for Such Coolers, Cooling
Effect, Cooler Construction and Materials, Advantages and
Disadvantages, Rotary Pad Evaporative Coolers, The Rotors,
Antiscaling and Anticlogging Features, Rotary Cooler Advantages and
Disadvantages, Rotary Drum Coolers, Review Questions.
X. COMBINED EVAPORATIVE COOLING SySTEMS ....... 163
"Add-On" Systems, Duct Size Problems, Add-On System Changeover,
"Piggy-Back" Units, A Residential Unit, "Make-up Air" Units, A Heat
Recirculation Method, The Future, Review Questions.
XI. AIR-WASHER EVAPORATIVE COOLERS ................ 174
Commercial Air Washers, Construction, Heating-Cooling Coils,
Airflow, Spray Arrangements, Nozzles, Other Aspects, New
Table of Contents / xi
Developments, Cooling Performance, Advantages and Disadvantages,
Cell-Type Air Washers, Construction, Capillary Cells, Wetting
Devices, Air Cleaning Effect, Evaporative Cooling Performance,
Trends, Review Questions.
XII. THE RIGID-MEDIA COOLERS .......................... 185
The New Materials, Rigid-Media Performance, Large Rigid-Media
Coolers, Large Cooler Uses, Exhaust-Type Coolers, Small Rigid-
Media Coolers, Add-On Pads, Vertical Counter-Flow Coolers, Review
Questions.
XIII. INDUSTRIAL PLANT COOLING ......................... 200
Industrial Trends, True Costs of Industrial Cooling, The Cooling
Opportunity, Refrigerative Factory Cooling, Ventilative Cooling,
Circulating Fans, Evaporative Cooling versus Ventilative Cooling,
Industrial Evaporative Cooling, Space or Room or Area Cooling,
Central Station Systems, Spot or Person Cooling, Spot Cooling
Outlets, Spot Cooling Accessories, a Special Case, Rules for Industrial
Evaporative Cooling, Cooling Load Control, Cooling System Design,
Space-Cooling Comfort, Spot-Cooling Comfort, Combined Systems,
The Future, Review Questions.
XIV. TEXTILE MILL EVAPORATIVE COOLING ................ 226
History, Materials and Processes, Primary Mill Humidification
Systems, Direct Humidification, Wet Ducts, Indirect Humidification,
Atomizing Power Consumption, Conversion to Evaporative Cooling,
Wet Duct Cooling, Dry Duct Cooling, New Looms, The New
Textiles, Central Station Evaporative Cooling, Cooling Performance,
Typical Mill Cooling Problems, Heating, Finishing Mills, Localized
Exhausting, Makeup Air Supply, Finishing Mill Evaporative Cooling,
Heating Finishing Mills, The Future in Textile Mills, Indirect Cooling,
Review Questions.
XV. ANIMAL AND POULTRY COOLING ..................... 247
Cooling Animals, Swine Cooling, Swine Cooling Systems, Controls,
Outdoor Swine Cooling, Cattle Cooling, Economic Results, Cow
Barns, etc., Poultry Cooling, Cooling Needs, General Results, a Drip-
Cooler Experiment, Exhaust Fans, a Slot Experiment, Economic
Results, Current Drip-Cooler Use, Alternative Systems, Special
Animal Houses, Systematic Ventilating and Heating, Pure Ventilating
Systems, Eivaporative Cooling Special Animal Houses, Other Animals,
Review Questiolls.
XVI. GREENHOUSE AND PRODUCE COOLING .............. 268
Tomatoes,OtherFood Plants, Specific Benefits, Flower Raising,
Greenhouse Cooling Systems, Wall Panel and Fan Systems, Wall
Pads, Temperature Effects, Heating and Ventilation, Controls, Food
Storage and Processing, Potatoes, Citrus Fruits, Other Products,
Review Questions.
XVII. DIRECT COOLER RATING AND SiZiNG ............ , .. . 283
Performance Measurement, Proposed Evaporative Cooler Rating
Units, Cooling Performance by Weighing, Sensible Heat Regain,