Hammond Heat Treatment for Insect Control

Developments and Applications
1. Auflage 2014
ISBN: 978-0-85709-781-1
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, Band 241, 120 Seiten

Reihe: Woodhead Publishing Series in Food Science, Technology and Nutrition

Stored product insects and other pests represent a major hygiene and safety issue to many industries, from food production to building infestation, and issues for timber pallets and packaging. Beds bugs are rapidly becoming a public health issue in hotels, hostels and houses in many parts of the world. While fumigation has been one of the prevalent routes for pest control, there remain issues with the toxicity of the chemicals used and potential exposure to humans therefore heat treatment has proven to be a successful alternative when used correctly. It is well known that excessive heat is dangerous to life. There is a difference between the amount of heat required to kill microbes such as bacteria and viruses and that required to kill larger life forms such as insects or mammals. This book focuses on the use of heat to kill insects and mites in food production, storage and other facilities. Heat Treatment for Insect Control examines how controlled heat treatment kills all stages of pest insect life across species and without causing damage to surrounding structures or electronics. The advantages of heat treatment include no health & safety hazards, a completely controllable and environmentally friendly process, reduced treatment time of fumigation (hours verses days), as well as no factory shutdown or exclusion of staff from adjacent areas during treatment. Part I reviews the principles of heat treatment, with chapters covering the fundamentals, planning, best practice and costs of integrated pest management. Part II looks at heat treatment applications in food production, storage, food materials and fresh produce. Part III examines the other applications in clothing, small rooms, buildings, and transportation. - Provides a comprehensive and systematic reference on the heat treatment for insect control - Reviews the development of heat treatment processes and technology as part of integrated pest management approaches

Dave Hammond BSc (Hons) is Managing Director of Thermokil, UK. With over 30 years' experience in the pest control industry, he has also worked as a pest control consultant around the world including in New Zealand, Australia, Israel and Romania.

Autoren/Hrsg.

Hammond, Dave

Leseproben

1 Fundamentals of heat treatment of insect pests
Abstract
It is well known that excessive heat is dangerous to life. There is a difference between the amount of heat required to kill microbes such as bacteria and viruses and that required to kill larger life forms such as insects or mammals. This book focuses on the use of heat to kill insects and mites in food production, storage and other facilities. Keywords Temperature Conduction Convection and radiation Energy 1.1 Introduction
Animals are made up of a combination of materials, including fat, bone, water, chemicals and proteins, the latter of which are largely amalgamated from amino acids. These proteins can be highly specialised, and range from structural proteins such as keratin (which makes up hair and fur) and haemoglobin (which carries oxygen and carbon dioxide in the blood) to antibodies and enzymes. Being quite fluid and complex in design, proteins are not generally heat stable and their functionality decreases sharply to the point of destruction at temperatures just outside the normal ranges of life on earth. Normal human body temperature is around 37 degrees Celsius (98.4 degrees Fahrenheit). Temperatures over 40 degrees Celsius are a potential risk to health. The reason for this is that the structures of the proteins in our bodies start to weaken and cease to function as they should. However, humans are able to endure extreme forms of heat, such as saunas, due to the high water content of the human body. This allows perspiration, incorporating the principle of latent heat of evaporation. In addition, the relatively large mass of humans compared to smaller animals and insects carries benefits in terms of specific heat capacity. These are two basic terms in heat dynamics that should be understood when trying to carry out heat treatments for pest control. Animals can also survive at high temperatures, for example in deserts at temperatures of over 50 °C, by avoiding the heat, moving about largely at night and living under the surface of the sand by day, thereby exploiting the insulation properties of the sand or rocks under which they hide. If desert animals need to move about on the surface by day, they do it very quickly and by minimising surface contact as far as possible before reaching a point of heat refuge. Typical avoidance techniques include the classic ripple movement of the sidewinder snake as it moves across the hot surface, keeping only two constantly changing points of contact with the hot sand, and lizards standing on the tips of just two legs at a time to keep away from radiated heat. Despite these avoidance techniques, a true core temperature of above 45 °C sustained for several hours will kill most complex forms of life, e.g. all vertebrates, most adult insects and other invertebrates. Some eggs or specialised diapausing or pupal states are more resistant and may require longer treatment. Just as heat causes damage to animals, it can also cause damage to whatever the target pest is living in, from food products to machinery, cars and other transport vehicles and building structures. The purpose behind this book is to guide pest control technicians in how to kill insects and mites in food processing, storage and other environments without damaging the infrastructure (e.g. building or machinery) or product in which the insects are living. In order to do this successfully, a basic understanding of heat dynamics is required. 1.2 Heat transfer: conduction, convection and radiation
Heat flows from hot to cold, and this movement is called energy transfer. Energy transfer can take place in the form of conduction, convection or radiation When a substance is heated up, its particles gain kinetic energy. In gases or liquids this means that the particles move around more quickly, in solids they vibrate more rapidly. If these particles are packed closely together in a dense, hard product like a metal, then as one vibrates it bumps into its neighbours, causing them to vibrate and so on down the line, causing the vibrations to move through the product. This movement of energy down the line or progressive heating is called conduction. The closer molecules are packed together, the quicker the process of energy transfer and the better the conductivity. Metals are good conductors of heat, plastic and wood less so, and items such as wool or fabrics are very poor, as each segment is linked by thin fibres separated by air, which, because it is a gas, is a good insulator. Conduction cannot be achieved in a gas, for example, because the molecules or atoms are dispersed, i.e. they are not physically touching each other. The movement from A to B of a given volume of hot air (or gas) is called convection. Convection can be forced, as in fan heaters or water pumps, or natural as in a home radiator system based on immersion heaters and radiators. In forced convection, air or water is heated up and forced along ducts or pipes from the energy source to the cold region. Here either the hot air displaces cold air to heat the area up, or hot liquid is passed through radiators, which cause convection by heating the air around them, causing it to rise and be replaced by colder air from below. Radiation involves the emission of electro-magnetic waves. Heat radiation is the emission of infrared energy, which is a type of radiation next to visible light in the electromagnetic spectrum. Infrared radiation is continually emitted or absorbed by matter depending on whether it is colder or hotter (respectively) than the background conditions. Radiation emission and absorption is also affected by colour, with black or dark colours being good emitters and absorbers of heat, while silver or light colours are poor absorbers and emitters because they reflect heat radiation. Infrared cameras are built to detect this form of radiation, with image signals converted into visible spectra, normally defined using a contrast between black (cold) and white (hot). In this respect, the greater the difference in temperature between the heat emitter and the background ambient temperatures, the better the image. So, for example, a man running hard over frosty ground at night without a coat (i.e. poorly insulated) will show up much more easily than the same man walking slowly wrapped up in a coat on a warm summer evening. 1.3 Measurement of energy
The basic unit of measuring temperature is on the absolute temperature scale: the degree Kelvin. This is the same basic unit as a degree Celsius except that, instead of starting at zero degrees C (the freezing point of water at standard temperature and pressure (STP)), the Kelvin scale starts at what is known as absolute zero where there is no energy at a molecular level, i.e. - 273 °C. It is important to be aware that Standard Temperature and Pressure (STP) are not even standard across the world – the International Union of Pure and Applied Chemistry (IUPAC) has STP as zero degrees C and absolute pressure of 100 kPa (14.504 psi, 0.986 atm). However, the National Institute of Standards and Technology (NIST) has STP as a temperature of 20 °C (293.15 K, 68 °F) and an absolute pressure of 101.325 kPa (14.696 psi, 1 atm). Power is measured in watts. Power is a reflection of the rate of doing work; 1 watt is 1 joule per second. Different heaters have different power ratings e.g. a 100 kW heater can produce 100 kJoules per second. Power = work done/time taken. As an example, if a heater passes out 6 kJ (6000 joules) in 2 minutes its power output will be: P = W/t ? 6000/120 = 50 watts. For electricity, the simple formula is: Power output (watts) = Volts × Amps. So from a single phase 230 v socket at 13 amps the maximum power is 230 × 13 = 2990 watts or 2.9 kWatts, which means the heater can provide 2900 joules every second. From a 415 v three-phase system on a 16 amp circuit breaker we could get 415 × 16 × 3 = 19 920 or 19.9 kW in total, minus the power needed for any fan units (leaves most three-phase heaters rated at 18–19 kW), or as sometimes termed: kVA (W = V × A). The potential calculations for heating something up are then complicated by the opposite powers trying to cool it down. Here the insulation properties of the building must be taken into account, or more specifically the relative cross section areas of different materials such as roof tiles, insulated walls, cladding, etc., all of which have different insulation properties. The temperature difference between the ambient temperature outside the heat treatment area and the slowly increasing temperature of the heat treatment area delta t, will also greatly influence the rate of cooling – the higher the delta t, the quicker a body will cool down. Heat treatment will plateau when the rate of temperature increase influenced by the power of the heaters is equal to the rate of heat loss as influenced by the delta t and the insulation effort. If you are doing a job that may be influenced by weather, e.g. in winter, you can influence the delta t by starting early and aiming to peak at midday when the day is at its warmest. If you leave the job until later in the day,...