Abstract
This work deals with a replacing the heating system of intercity buses, made by long heat exchangers distributed on the sides of the passenger saloon by small and compact ones that use forced convection to heat dissipation. At the beginning the calculation was made of the heat capacity of a heat exchanger with the parameters defined by the supplier, and then conducted an analysis of change in these parameters in order to improve its efficiency. The method for examining the heat exchanger is based on the correlations available in the convection flow inside and outside to determine the respective convective coefficients, and therefore the overall coefficient of heat transfer. Following, the heat exchanger in its original form, was tested on bench. Thus, from the thermal load of the bus model studied, the amount of exchangers required has been defined to satisfy the thermal comfort of passengers. Field tests of the heating systems with new heat exchangers were performed to obtain actual data of the proposed system. The original factory system showed to be efficient in meeting the needs thermal load and economically viable, such that the critical thermal load can be met with ten heaters installed along the body. Furthermore, this system offers the possibility of varying the parameters to best fit to the project, where the flow variation of the fans or the spacing between the fins of the heat exchanger decreases the amount of heaters required. At the same time, the system showed the need for further study to assess its distribution along the passenger saloon in order to meet a best uniformity temperature distribution. http://dx.doi.org/10.18226/23185279.v3iss1p29
Highlights
This work deals with a replacing the heating system of intercity buses, made by long heat exchangers distributed on the sides of the passenger saloon by small and compact ones that use forced convection to heat dissipation
Dentre os quais Stedile [3] buscou a melhoria do isolamento termico, propondo alteracao nos materiais utilizados e obteve reducao de pontes termicas ao longo da carroceria, bem como reducao da perda de temperatura interna
Os testes em campo devem ser realizados em um veıculo com sistema de calefacao instalado, revisado e aprovado pelo controle de qualidade da empresa, e executados segundo as determinacoes internas da empresa, dentre as quais, as principais exigencias sao:
Summary
Cada dia mais tem crescido a preocupacao dos fabricantes de veıculos com o conforto dos usuarios, o que estarelacionado a aspectos ergonomicos de assentos, conforto. Sao muito empregados os trocadores de calor de correntes cruzadas lıquido-gas [7], cuja superfıcie de troca termica do lado gas pode ou nao ser estendida (aletas). No caso dos trocadores de calor de superfıcie estendida, as aletas sao montadas sobre sua superfıcie primaria (tubos ou placas) e sobre as quais escoa um gas, em que o coeficiente de conveccao emuito baixo comparado ao dos lıquidos. Para os trocadores de calor tipo tubos aletados, as aletas mais comuns sao as circulares planas e contınuas planas, onduladas, com recortes, etc. Desta forma, o autor utilizou um novo parametro de projeto, dado pela razao entre o coeficiente de transferencia de calor e a perda de carga do escoamento atraves dos tubos, determinando um diametro ideal para eles. Os coeficientes de transferencia de calor por conveccao se basearam em correlacoes encontradas na literatura
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