Frost Protection: fundamentals, practice, and economics Volume 1 (original) (raw)
Related papers
Frost protection: fundamentals, practice and economics. Volume 2
2005
for their friendship and support during visits to FAO in Rome. Some thanks are due to Professors Donatella Spano and Pietro Deidda in the Dipartimento di Economia e Sistemi Arborei for providing encouragement and facilities during part of the book preparation at the University of Sassari, Italy.
Principles of Frost Protection
More economic losses occur due to freeze damage in the United States than to any other weather related hazard. Consequently, considerable effort to reduce damage is expended. The cost effectiveness depends on the frequency of occurrence, cost of the production method, and the value of the crop. Generally, passive freeze protection is easily justified. Passive protection includes practices done before a freeze night that reduces the potential for damage. Active protection includes energy intensive practices (heaters, sprinklers, wind machines, etc.) that are used during the freeze night to replace natural energy losses. Active protection is sometimes not cost effective. In this lecture, forecast freezing temperatures and passive protection will be discussed. TYPES OF FROST EVENTS Advection Frost An advection frost occurs when cold air blows into an area to replace warmer air that was present before the weather change. It is associated with moderate to strong winds, no temperature inversion, and low humidity. Often temperatures will drop below 32°F (0°F) and stay there all day. Advection frosts are difficult to protect against, but fortunately they are rare in California fruit growing regions. occurs when the temperatures aloft are only slightly higher than near the surface. When there is a strong inversion (low ceiling), temperature increases rapidly with height. Most frost protection methods are more effective during low ceiling, strong inversion conditions. ENERGY TRANSFER Energy or heat transfer determines how cold it will get and the effectiveness of protection. The four methods of energy transfer are radiation, conduction, convection, and latent heat. Understanding these heat transfer mechanisms is extremely important for good frost protection management. Radiation Radiation is electromagnetic energy transfer. A good example of radiation is sunlight. Because it is very hot, considerable energy is radiated from the sun to Earth. Although much cooler, objects on Earth also radiate energy to their surroundings. If an object radiates more energy than it receives from other sources, it will cool. Conduction Conduction is heat transfer through matter where the objects do not move. A good example is the transfer of heat through a metal rod if one end is placed in a fire. The heat is transferred by conduction to the other end of the rod. Conduction is important in soil heat transfer and hence frost protection. Convection Convection is the process where a fluid (e.g. air or water) is heated and physically moves from one place to another and takes heat with it. Air heated by smudge pots is an example of convection because the air, warmed by the heaters, rises and mixes with colder air in the orchard to raise the temperature. Smudge pots also radiate heat to nearby trees but the main protection comes from convection. Latent Heat When water condenses, cools, or freezes, the temperature of the environment around the water rises because latent is changed to sensible heat. Latent heat is chemical energy stored in the bonds that join water molecules together and sensible heat is heat you measure with a thermometer. When latent heat is changed to sensible heat, the air temperature rises. When ice melts, water warms, or water evaporates, sensible heat is changed to latent heat and the air temperature falls. Table 1 shows the amount of heat consumed or released per unit mass for each of the processes. Process Heat Exchange Calories per gram Water cools from 20 o C (68°F) to 0 o C (32°F) +20.0 Water freezes at 0°C (32°F) +79.7 Ice cools from 0°C (32°F) to-5 °C (23°F) +2.5 Water evaporates at 0 °C (32 °F)-597.3 Water condenses at 0 °C (32 °F) +597.3 Water sublimates (ice to water vapor) at 0 °C (32 °F)-677.0 Water deposits (water vapor to ice) at 0 °C (32 °F) +677.0
Frost Hardiness Testing: An Ontario Update
In the early 1980s large losses of outdoor-overwintered conifer container seedlings were not uncommon in Ontario . These losses occurred because seedlings were placed outside in the fall while actively growing and before they were adequately hardened off. Even mild frosts could cause damage and in some cases entire crops were lost ( ). To address these losses, frost hardiness testing methods were developed to provide nursery managers a tool by which to determine when their trees are hardy enough to withstand fall frosts ).
Use of Insulation for Frost Prevention, Jackman Airport, Maine, 1986-1987 Winter
1991
Design, Construction and Operations Technology for Cold Regions; Task BS, Base Support; Work Unit 036, Improved Pavement Design Criteria in Cold Regions. This report was technically reviewed by Hisao Tomita (FAA) and Wendy Allen (CRREL). The authors thank Richard Guyer for instrumentation installation and data collection, Marcia VanCamp for collecting data, Blair VanCamp for assisting in equipment installation, and Pamela Bosworth for typing the manuscript. The contents of this report are not to be used for advertising or promotional purposes. Citation of brand names does not constitute an official endorsement or approval of the use of such commercial products. CONTENTS
International Journal of Horticultural Science, 2011
Frostbuster is a new system, engine and technology, developed to protect fruit plantations from the frost damage. In order to raisedomestic experiences and measurements, experimental approach has been initiated to prove the utility of the system under excessively lowtemperature in the plantation of the Siófoki Gyümölcstermesztési Zrt (Fruit Growing Co. Siófok). The first opportunity ensued in the night ofFebruary 23-24, 2011, when the temperature sank to 12°C below zero. The question was to see whether we could prevent the drop oftemperature by the frostbuster technique. The margin of an anticyclone staying on East Europe secured a stable condition to make tests. Theonly difference from the imaginable conditions of dangerous frosts was the heat keeping capacity of trees was weak, much inferior thancompared with trees in full boom. As a consequence, the tree rows represented much lower heat-capacity and cooled down much quicker thanblooming trees in springtime, i.e. their temperature...
Frost Resistance of Building Materials : Proceedings of the 2nd Nordic Research Seminar in Lund 1996
Report TVBM, 1996
Frost destruction of porous building materials is a big problem in the Scandinavian countries, and in many other countries inside and outside Europe, such as U.K., Germany, countries in eastem Europe, U.S.A., Canada, etc. Much research has been devoted to solving the frost destruction problem, especially conceming the destruction of concrete, but also conceming the destruction of clay brick, roofing tile, cellular concrete, natural stone, etc. Nordic researchers have made important contributions in the past; names such as Poul Nerenst in Denmark, Sven Gabriel Bergstrom and Birger Warris in Sweden, and Jukka Vuorinen in Finland can be mentioned. Previously, frost damage was in most cases of type internai damage occurring when the "stone" was frozen in a more than critically saturated condition. During the last decades, surface scaling of concrete is a growing problem in many countries. The reason is an increased use of deicing salts on roads and bridges. Maybe, surface scal...
Correct simulation of real frost attack in laboratory tests
ConcreteLife'06-International RILEM-JCI Seminar on Concrete Durability and Service Life Planning: Curing, Crack Control, Performance in Harsh Environments, 2006
In another contribution to this symposium [1] the author showed that frost suction is the most important phenomenon in any freeze-thaw attack. It precedes the damages due to frost action. It is far more efficient than any other transport e.g. like isothermal capillary suction. It is linked to the transient and combined heat and liquid transport during a freeze-thaw cycle. The boundary conditions are extremely important. When reproducing real conditions in laboratory testing the boundary conditions of real attack must be simulated with care. In the RILEM recommendations of CDF and CIF test this prerequisite is consequently fulfilled for the first time. Due to this they are efficient and precise procedures approved following ISO 5725. These tests allow simultaneously the determination of capillary and frost suction, the internal damage and the scaling. Scaling dominates in the combined attack of frost and deicing chemicals, internal damage in pure frost attack. The frost suction could be used to measure the transport of other detrimental substances dissolved in water and transported with it e.g. of chlorides.
Evaluation of a frost accumulation model
Meteorological Applications, 2003
Formation of frost on paved surfaces presents a potential hazard to the motoring public in cold climates. Temperatures of the paved surface are not measured routinely by the National Weather Service and are not part of public forecasts of winter conditions, yet highway maintenance personnel must make frost suppression and anti-icing decisions based on expectations of future paved-surface temperatures. The Road Weather Information System measures road surface, air and dew-point temperatures, road surface conditions, and wind data at numerous locations in the state of Iowa and reports the data in real-time to maintenance offices. A model based on simple concepts of moisture flux to the surface was developed that uses data from roadway weather stations or forecasts of dew-point temperature, air temperature, surface temperature and wind speed to calculate frost accumulation on bridge decks in Iowa. The analysis showed that the model has sufficient accuracy to be used as an operational tool for assessing frost accumulation on bridge decks. A logistical regression procedure was developed to determine the probability that a maintenance worker will observe frost for a given calculated frost depth.