No abstract

Pig farming is a sector of animal husbandry, the development of which is great attention. The pork market occupies a large share in the trade in animal products. In the conditions of they do competition more efforts are made to improve the quality and reduce the cost of production. To achieve this goal, work is being done in several areas – development and expansion of the gene pool, improvement of the living environment in the premises for animal husbandry, reduction of energy costs. Along with the development of feeding technologies, it is necessary to create a suitable microclimate in the premises, in which the animals to realize their productive potential, which in turn is directly related to the use of heating and cooling systems. The design of these systems for both existing and new buildings is carried out according to generally accepted methodologies, which in turn require time for calculation and use of specialized software. The methodologies for determining the loads for heating and cooling of livestock buildings, in accordance with the current legislation in the Republic of Bulgaria, are compared with a new method proposed in this publication. The possibility to consider a livestock building from the point of view of the theory of heat exchange allows the use of the basic differential equations describing the dynamic interaction of the building with the environment. This description would be complete and complex to implement. Therefore, the method of dimensional analysis is used, which is based on generalized indicators, when fulfilling certain criteria of similarity. The aim of the new methodology is to shorten the design time and allow the rapid sizing of heating and cooling systems in livestock buildings. In developing the new methodology, the task was the proposed new approach to summarize the interaction of all physical parameters affecting the heat exchange between the building and the surrounding air, allowing to take into account changes in external (air temperature, wind speed, solar radiation intensity) and internal factors (heat given off by farm animals, lighting, process equipment and processes) affecting the heat exchange between the building and the ambient air

As a result of the development of industrial organic synthesis, the output of secondary processes in oil processing is becoming increasingly diverse. Production volume is a nodal indicator that is limited by the available production capacity, equipment configuration and the monetary equivalent of energy costs. In order to determine the technological potential and cost of produced petroleum products, it is necessary to create a complex that includes all stages of production. The most important criterion for evaluating the energy efficiency of an oil refinery is the relative energy consumption, which depends on its complexity. This criterion can be presented as a set of the different types of energy resources used in the course of production and applied to the total production. For this pur-134 pose, the energy resources invested in the given technology should be referred to a finished product or raw material. The peculiarity of oil refineries is that, due to the variety of oil derivatives, energy consumption, as a set of different installations, is much more appropriate to relate not to individual target products but to the amount of processed oil. In practice, all types of energy carriers must be converted to an equivalent value. This paper provides an in-depth analysis of the energy costs of oil refineries. The collection of energy flows of different types and dimensions is the subject of the present study. Based on this, a method is presented that allows a comparison of the energy efficiency of refineries with different capacity and configuration of crude oil processing stages based on the energy index and the equivalent distillation performance.

The article discusses and analyses the factors related to the use of a thermal imaging camera to determine heat loss in industrial steam pipelines at factories from chemical and metallurgical industry, by measuring their surface temperature. The generally accepted enthalpy method for determination of the loss has serious drawback it gives accurate results, but in averaged units in which it is impossible to take account of the contribution of the different parts and components of the pipeline in the total heat loss. The unavailability of information on where, how and in what way along the route this loss is formed does not allow prompt and specific measures to be taken for its reduction. An attempt has been made to structure empirically a reliable analytic dependence for determination of the heat exchange coefficient, bringing together the various factors influencing the heat exchange. By the method of the least squares the free coefficient and the exponent have been determined of criterion equation satisfying initial and boundary conditions of the experiment. Based on the obtained results for determining the heat losses by measuring the surface temperature of steam pipelines with a thermal imaging system, a reliable and acceptable method is proposed, which has a place in engineering practice. For this purpose, an industrial experiment has been carried out at three actually operating steam pipelines of different diameters and steam parameters. A criterion equation has been derived that can be used as a mathematical model for software products with a practical orientation for regular assessment of heat losses of steam pipelines. Values of heat losses determined through energy balance of heat carrier and heat flux from the outer surface of the steam pipelines have been compared. Results for the heat exchange coefficient, obtained through a balance have been compared with the analytically determined values based on current standards. A new method has been developed for express evaluations of the current heat losses of the steam pipeline in real time, as the sum of the losses through its individual components gives as average values 9÷12 % increased results for the losses compared to the enthalpy method. Its great advantage is that it can be used selectively to determine the losses through individual sections of the steam pipeline.

Increasing consumption of meat and meat products worldwide is closely linked to improving the living environment for livestock. According to zoo experts, the appropriate microclimate in buildings leads to improved metabolic processes in their cultivation and contributes to their rapid weight gain. The issue of raising new-borns and young animals is especially relevant. Achieving optimal parameters of the microclimate in the premises, together with the necessary veterinary care for new-borns reduces stress and mortality in them. The above requires the implementation of new and modern engineering solutions in the design and construction of livestock buildings. The use of numerical simulations, through CFD programs for modelling and solving engineering problems, as well as the creation of adequate mathematical models, is a prerequisite for reducing the time and resources to solve a problem. Based on the accumulated experience of the authors on the microclimate in livestock farms in this publication, a numerical simulation of air exchange in a livestock building for breeding sows with young piglets is presented. The physical model, research and analysis are realized in the middle of Ansys Fluent. Two models of air exchange organization in the livestock building are proposed. The obtained data on the temperature and speed fields in the building will lead to an improvement of the microclimate in the considered site. In addition, they could serve as a basis for conducting the next series of computer simulations. The built models can be adapted for other building constructions for breeding other types of animals. The analysis of the data and a more in-depth examination of the factors related to animal husbandry could help to increase pork yields on livestock farms