Call number: LD2668 .T4 1933 L41

South Africa contributes approximately 0.5 percent to the total world milk demand and is the third largest producer of fresh cow milk in Africa after Sudan and Kenya. In comparison to any other enterprise, the cost of milk production is influenced by numerous factors, that in turn affect the profitability of the farm enterprise; however one of such factors is high electricity cost. In this regard, there is need for efficient operation of the milk processing plant at all stages and at the same time maximising on product quality and minimising on the cost of production including energy. At the dairy farm, milk handling mainly commences as the milk leaves the cow udder at 35°C–37°C and must be cooled rapidly to a storage temperature of 4°C in a bid to stop microbial activity. The cooling of the milk can be done directly by the bulk milk cooler (BMC) from 37°C to the required storage temperature of 4°C or it can be done successively through pre-cooling. The process of pre-cooling involves the use of a heat exchanger where in most instances the plate heat exchanger (PHE) is used as the pre-cooler (PC) thereby leading to energy savings in a dairy facility. Cooling of milk involves significant amount of energy and it could account for about 20 percent of the total energy consumed on a farm. The aim of the research was to develop mathematical models that could be used to predict the electrical energy performance and capture the cooling saving of an on-farm direct expansion bulk milk cooler (DXBMC) during the milk cooling process. Accordingly, data acquisition system (DAS) was designed and built to accurately measure the power consumption of the BMC, temperature of raw milk, room temperature, temperature of cold water, relative humidity and ambient temperature. The volume of milk produced per day was extracted from the daily records on the farm. In addition, the temperature sensors were connected to a four channel HOBO data loggers which were configured to log at every five-minutes interval. The results were analysed and the mathematical models were developed using MATLAB. The statistical Toolbox in MATLAB was used to rank the predictors according to their weight of importance using the ReliefF Algorithm test. The results showed that on average, the daily electrical energy consumed by the BMC at the two milking times was higher during the peak period (127.82 kWh and 93.86 kWh) than the off-peak period (48.31 kWh and 43.23 kWh). On average, the electricity used for cooling of milk on the dairy farm was 17.06 kWh/m3 of milk. The average monthly electricity used per cow on the farm was 8.03 kWh/cow which translated to an average of 0.26 kWh/cow/day The average specific energy consumption of the cooling system per litre of milk cooled was 0.02 kWh/L and was almost constant throughout the whole period of monitoring. Furthermore, the BMC was able to cool 57.33 L/kWh during the off-peak period which increased by 7.7 percent to 62.13 L/kWh during the peak period. Furthermore, mathematical models represented as multiple linear regression (MLR) models were built and developed using the experimental data. The developed mathematical models had good agreement with the experimental data as evidenced by the correlation coefficients of 0.922 and 0.8995 along with 0.935 and 0.930. The ReliefF Algorithm test revealed that the volume of milk was the principal contributor to the energy consumption of the BMC for both the morning (AM) and afternoon (PM) milking period. The Relative Prediction Error (RPE) was used to evaluate the suitability of the developed models. In this light, the AM off-peak model had RPE of 18.54 percent while the PM off-peak model had 14.42 percent. In addition, the AM peak and PM peak models had RPE of 19.23 percent and 18.95 percent respectively. This suggested that the MLR models for the off-peak and peak milking periods (both AM and PM) had acceptable prediction accuracy since the RPE values were between 10 percent and 20 percent. The findings from the experimental study showed that the coefficient of performance (COP) of the AM milking period was higher (2.20) than that of the PM milking period of the BMC (1.93). Increase in the milk volume led to an increase in the COP such that the peak period with higher milk volumes recorded a high COP increase of 12.61 percent and 19.81 percent for the AM and PM milking periods respectively.

Orientador: Paulo César Razuk / Banca: Augusto Ronchi Junior / Banca: Waldemar Gastoni Venturini Filho / Resumo: O produtor de leite de cabra, com o apoio e incentivo de entidades governamentais, privadas e ONGs; agrega tecnologia ao leite garantindo uma melhor distribuição de renda e qualidade de vida, fixando-se cada vez mais no campo. O resfriamento do leite após a ordenha é a melhor medida para retardar a proliferação natural das bactérias e sua temperatura deverá ser reduzida de 36 ºC para 4 ºC no período máximo de 2 horas em cada ordenha. O tempo transcorrido entre a primeira ordenha e seu recebimento na usina de beneficiamento deverá ser, no máximo, de 48 horas. Neste trabalho propõe-se projetar e analisar tanques de resfriamento de leite com capacidades úteis de 320, 500 e 2000 litros em aço inoxidável austenítico AISI 304, utilizando-se do coeficiente global médio (U) e das temperaturas médias de saturação do fluido de refrigeração (X) obtidos em ensaios experimentais. Um objetivo secundário foi verificar a possibilidade da utilização de caixas d'água de polietileno com a mesma capacidade dos tanques, por ser um produto acessível, de baixo custo e que atende as exigências sanitárias, visando obter um produto que possa substituir o aço inoxidável, mas descartou-se esta possibilidade, pois o fundo plano destas caixas dificultaria a retirada do produto e a limpeza. Nos cálculos envolvidos na geometria para a construção dos tanques, utilizou-se da relação entre a altura cilíndrica e o diâmetro que contemplasse respectivamente, o número... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The goat milk producer, with support and encouragement of governmental and private agencies as well as NGOs, aggregate technology to milk production ensuring a better distribution of income and life quality for all his family, making it possible the maintenance of the country life. The milk cooling ater the milking process is the best alternative to delay the natural proliferation of bacteria. The milk temperature should be reduced from 36 ºC to 4 ºC in a maximum period of time of two hours for each milking. The elapsed time between the first milking and the milk delivery in the processing plant shall be at most 48 hours. In this work, we propose to design and analyze milk cooling AISI 304 austenitic stainless ateel 320, 500 and 2000 liters tanks, using the mean global coefficient (U) and mean saturation temperatures of the refrigeration fluid (X), obtained experimentally. Besides stainless steel built tanks, accessible low cost polyethylene watertanks, with same dimensions of the steel tanks, attending the necessary sanitary requirements were used, aiming for an alternative product that can replace stainless steel. However, this possibility was rejected, because its flat basis would make it hard the product removal and its cleaning. During the geometric calculations in the manufacturing of the tanks, the relationship betwwen the cylindrical height and the diameter was defined in order to provide the golden ratio and batch square... (Complete abstract click electronic access below) / Mestre

Made available in DSpace on 2014-06-11T19:25:27Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-03-24Bitstream added on 2014-06-13T18:26:32Z : No. of bitstreams: 1 salvadeo_vm_me_bauru.pdf: 454404 bytes, checksum: f9533c97cafb5b981d239b02a0bf9213 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O produtor de leite de cabra, com o apoio e incentivo de entidades governamentais, privadas e ONGs; agrega tecnologia ao leite garantindo uma melhor distribuição de renda e qualidade de vida, fixando-se cada vez mais no campo. O resfriamento do leite após a ordenha é a melhor medida para retardar a proliferação natural das bactérias e sua temperatura deverá ser reduzida de 36 ºC para 4 ºC no período máximo de 2 horas em cada ordenha. O tempo transcorrido entre a primeira ordenha e seu recebimento na usina de beneficiamento deverá ser, no máximo, de 48 horas. Neste trabalho propõe-se projetar e analisar tanques de resfriamento de leite com capacidades úteis de 320, 500 e 2000 litros em aço inoxidável austenítico AISI 304, utilizando-se do coeficiente global médio (U) e das temperaturas médias de saturação do fluido de refrigeração (X) obtidos em ensaios experimentais. Um objetivo secundário foi verificar a possibilidade da utilização de caixas d'água de polietileno com a mesma capacidade dos tanques, por ser um produto acessível, de baixo custo e que atende as exigências sanitárias, visando obter um produto que possa substituir o aço inoxidável, mas descartou-se esta possibilidade, pois o fundo plano destas caixas dificultaria a retirada do produto e a limpeza. Nos cálculos envolvidos na geometria para a construção dos tanques, utilizou-se da relação entre a altura cilíndrica e o diâmetro que contemplasse respectivamente, o número... / The goat milk producer, with support and encouragement of governmental and private agencies as well as NGOs, aggregate technology to milk production ensuring a better distribution of income and life quality for all his family, making it possible the maintenance of the country life. The milk cooling ater the milking process is the best alternative to delay the natural proliferation of bacteria. The milk temperature should be reduced from 36 ºC to 4 ºC in a maximum period of time of two hours for each milking. The elapsed time between the first milking and the milk delivery in the processing plant shall be at most 48 hours. In this work, we propose to design and analyze milk cooling AISI 304 austenitic stainless ateel 320, 500 and 2000 liters tanks, using the mean global coefficient (U) and mean saturation temperatures of the refrigeration fluid (X), obtained experimentally. Besides stainless steel built tanks, accessible low cost polyethylene watertanks, with same dimensions of the steel tanks, attending the necessary sanitary requirements were used, aiming for an alternative product that can replace stainless steel. However, this possibility was rejected, because its flat basis would make it hard the product removal and its cleaning. During the geometric calculations in the manufacturing of the tanks, the relationship betwwen the cylindrical height and the diameter was defined in order to provide the golden ratio and batch square... (Complete abstract click electronic access below)

M.S.

The following conclusions appear to have merit: 1) The heat obtained from cooling milk in a mechanical farm milk cooler may be used for preheating a quantity of water. 2) The amount of water heated and the temperature to which it is heated are functions of the heat obtainable from the milk cooler and refrigeration equipment. 3) The percentage of available heat from the condenser that is available in the water passed to the electric water heater is a function of: (a) the design of the condenser-to-water heat transfer system, (b) the size and shape of the storage tank, and (c) the losses from the storage tank. 4) The savings in cost of electric energy for operation of the electric water heater are appreciable when heat extracted from cooling milk is used to pre-heat water. In this study, the savings amounted to slightly more than 30 percent. However, a large quantity of heated water passed to the overflow tank. A savings of 54 percent could be realized when the water drawn from the pre-heat tank into the water heater was raised from 62 F - 120 F in the pre-heat tank. 5) Without the assistance of a competent refrigeration mechanic, the technical problems involved make it inadvisable for the individual farmer to attempt a conversion of current milk cooling equipment for the additional function of heating water. 6) This study indicates that greater savings may be effected with a refrigeration unit and condensing unit specifically designed for heating water, using the basic principles outlined in this study. / Master of Science

Made available in DSpace on 2014-07-29T15:08:14Z (GMT). No. of bitstreams: 1 Eric Nery Chaves.pdf: 1402393 bytes, checksum: eb28c97ecabfcf07a31c7bf35ab01e85 (MD5) Previous issue date: 2010-06-17 / This work presents the application of control techniques to drive single-phase induction motors with the aim of improving the performance of cooling systems. The control system is based on Fuzzy Logic and is applied to a three-phase PWM inverter adapted to drive singlephase motors with volts per hertz technique. The main feature of the work is to control the temperature of the cooling system driven by a hermetic compressor using variable speed. A commercial milk cooling system is used to obtain the results. / O presente trabalho demonstra os efeitos da aplicação de técnicas de controle em acionamento de motores de indução monofásicos, visando à melhoria do desempenho e eficiência energética, no local onde esses motores são aplicados. O trabalho em questão trata de um sistema que engloba um controlador de temperatura baseado em Lógica Fuzzy ou Nebulosa e um conversor de frequência trifásico, chaveado no modo PWM (modulação por largura de pulsos na sigla em inglês) senoidal, com controle escalar do tipo V/f (tensão proporcional à frequência) e adaptado para utilização em motores de indução monofásicos. O objetivo geral deste trabalho é o projeto e implementação de um sistema de controle de temperatura Fuzzy, com acionamento do compressor hermético em regime de velocidade variável. Também chamado de VCC (compressor de capacidade variável na sigla em inglês) - pois a capacidade é diretamente proporcional à velocidade - a estratégia de controle, a partir do acionamento do motor monofásico em regime de velocidade variável, será aplicada a um sistema de refrigeração que simula um tanque de resfriamento de leite e atenderá às Instruções Normativas nº 51 e nº 53, do Ministério da Agricultura, Pecuária e Abastecimento.