CC BY
22
Научни трудове на Съюза на учените в България-Пловдив. Серия В. Техника и технологии, естествен ии хуманитарни науки, том XVI., Съюз на учените сесия "Международна конференция на младите учени" 13-15 юни 2013. Scientific research of the Union of Scientists in Bulgaria-Plovdiv, series C. Natural Sciences and Humanities, Vol. XVI, ISSN 1311-9192, Union of Scientists, International Conference of Young Scientists, 13 - 15 June 2013, Plovdiv.
HEAT-EXCHANGERS - PASTEURIZATOR
Author: Meri Ilijoska Supervisor: Prof. Dr. Vangelica Jovanovska University „Kliment Ohridski" Bitola, Faculty of Biotechnical Sciences Email: meri_ilijoska@hotmail.com
Abstract
Heat-exchangers are thermal devices (appliances) which perform heat exchange between fluids, in order to create the heating or cooling of the fluid with one another. Often flow is realized as a combination where the two fluids move in different patterns combined by same-way, opposite-way and cross flow, thus creating different temperature profiles. There are also many types of heat-exchangers which are different in their construction and operation (tubular, plate and spiral). The heat-exchangers include pasteurizators, which are devices for pasteurization in order to destroy bacteria that can cause disease. There are many kinds of pasteurizators including: plate, drum or electric pasteurizators.
ШШ
llWb . L IJJ1I II
KOMOHA
>>РШ1Ш7Ч
rrf.^*
- PRC
1 tank
2 input
3 paddle
4 slot
5 tube
6 drum
7 Body
8 spiral ribs
9 out
ВСНГМО
Introduction Heat-exchangerisadevicebuiltforefficientheattransferfromonemedium
to another. It is widely used for heating, cooling, air conditioning, etc. A classic example of a heat-exchanger is located in the internal combustion engine in whichthe fluid circulates and allows cooling. As well the heat-exchangers are thermal devices, in which the exchange of heat between two fluids is made to allow heating or cooling of the fluid with one another. The main classification of the heat-exchangers is towards the specifics of the type of the heat exchange, such as:
Recuperative which are commonly used when the fluids are separated by a solid partition in which is the exchange of heat happens, with no physical contact between the fluids.
Regenerative in which periodically leaks the warmer fluid through the heat-exchange surface, that transfers the heat upon the elements from the heated heat-exchange surface. Then through the same heat-exchange surface the cooler fluid yields. This process is repeated periodically.
Interactional where the two fluids are in direct contact. The fluids may be liquid, liquid and gas, or gas and solids in dispersion form. The exchange of heat happens by mixing (for liquids that are soluble in one another), or by mechanisms of convection and diffusion through touch (intermediate) surface of contact between the two fluids.
Types of heat-exchangers
Tubular heat-exchanger
The tubular heat-exchanger consists of a series of tubes. One set of these tubes contains the fluid that must be either heated or cooled. The tubular heat-exchangers are typically used for high pressure (pressure greater than 30 bar and heat greater than 260°C). There are several types of features that should be taken into account when designing the tubular heat-exchangers and they include: the pipe diameter, the thickness of the pipe, the length of the pipe.
Figure 1. Tubular heat-exchanger Plate heat-exchanger
The plate heat-exchanger consists of a set of plates of stainless material that are merged into a single framework. In this framework there can be found a few sections that are taking various stages of processing, such as preheating, heating, maintaining the temperature for a certain time and cooling. The heating result can be vacuum steam or hot water, and the cooling result can be cold water, ice water or brine depending on the desired product.
Figure 2. Plate heat-exchanger Spiral heat exchanger
The spiral heat exchanger consists of two steel sheets or some other metal that must have given space and each must be coated and placed in a cylindrical package, where the inner part consists of two concentric channels.
1
Figure 3. Spiral heat-exchanger Pasteurizator
The pasteurizator is a device used for pasteurization, it performs a certain procedure of processing the food in order to destroy the bacteria that can cause disease. Pasteurized milk is the most common pasteurized food, but the pasteurizator can be used for other liquids and foods that should pass the pasteurization process. The Pasteurizator is used to make food safer, so that it can be sold commercially without concern that people will get sick when they consume it.
Types of pasteurizators
Plate pasteurizator
In the plate pasteurizator there are several sections carried out: in the first section the liquid product (milk) is heated to a temperature of pasteurization. Then the heated milk is flowing through a section to keep the temperature of processing, in order to obtain the required time. From this section the milk passes in the cooling section, which is cooled to +4t.
Figure 4. Plate pasteurizator Drum pasteurizator
The drum pasteurizator is composed of tank, body and a drum with blades for ejecting milk. The milk is brought by the pump in the space between the drum and the body. Under the influence of spiral ribs the milk moves up, in that way it is heated to the necessary temperature and with the help of the blades it is disposed in separate tubes to different machines.
70
1 pump
2 bowl milk
3 regenerator
4 regenerator
5 controller
6 tubular containment
7 electrode
8 chamber
9 ringlike Chamber
10 tube
Figure 5. Drum pasteurizator Electric pasteurizators The electric pasteurizator operates using electricity with low voltage. It gives best results at a temperature of 501, without changing the physical - mechanical properties of the milk.
Figure 6. Electric pasteurizator
References:
http://en.wikipedia.org/wiki/Heat_exchanger
http://www.tehnologijahrane.com/forum/tema/pasterizator
http://en.wikipedia.org/wiki/Shell_and_tube_heat_exchanger
