จำนวน Repository ( 16 )

การศึกษาพฤติกรรมการถ่ายโอนความร้อนในระบบเบรกเพื่อกำหนดค่าการนำความร้อนของผ้าเบรกที่เหมาะสม
การศึกษาพฤติกรรมการถ่ายโอนความร้อนในระบบเบรกเพื่อกำหนดค่าการนำความร้อนของผ้าเบรกที่เหมาะสม

Brake pad is a one of products that plays a role in the automotive parts industry and directly affects safety. Therefore there are many designs of brake pads for product development. This research aims to study the thermal conductivity of brake pads and define the thermal conductivity that appropriate to brake pads and also solve the problem of deterioration of braking automotive parts. To achieve this the 3 different ingredient brake pads from Compact International (1994) Co. Ltd. are studied in terms of the heat transfer behavior. The experimental work was set by simulating a brake on the single dynamometer at the braking speed of 50 100 and 130 km/h. As a results the significant parameters are copper and fillers respectively. It affects the heat transfer behavior by means of applying heat from the contact area between the brake pad and the brake disc to the caliper This knowledge will be used in the design of brake pad ingredients to determine the appropriate conductivity of the brake pads.

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การศึกษาพฤติกรรมการถ่ายโอนความร้อน และการสั่นสะเทือนของจานเบรกแบบตรง/แบบกลับที่ส่งผลกระทบต่อความสามารถการเบรก
การศึกษาพฤติกรรมการถ่ายโอนความร้อน และการสั่นสะเทือนของจานเบรกแบบตรง/แบบกลับที่ส่งผลกระทบต่อความสามารถการเบรก

The purposes of this study were to investigate the heat transfer and the vibration characteristics caused by front and back vented brake disc which had physically different shapes affecting braking distance. In accordance with the theory of heat transfer the heat transfer rates of two types of brake disc were different and played an important role in the deformation during usage. The single dynamometer was conducted to the experimental work as an engineering tool with boundary conditions according to JASO C406 standard. One degree of freedom (DOF) acceleration signals on the brake caliper were analyzed. The results obviously discovered that the back vented brake disc was able to reduce the vibration up to 43.5% comparing to the front vented brake disc in case of the braking temperature 200C initial breaking speed 50 km/h and the hydraulic pressure of 4 MPa. Besides the hydraulic pressure at 4 MPa generated the maximum vibration. Furthermore the initial braking speed and the braking temperature were also the important factors. Regarding braking distance results the results of the experimental work obviously discovered that the back vented brake disc created braking distance shorter than front vented brake disc. Besides there were important factors as braking temperature hydraulic pressure and initial speed of braking. Especially the high braking temperature caused an increase of deceleration and a decrease of braking distance. Moreover the high hydraulic pressure produced a deduction of braking distance and an increase of deceleration. Finally the initial speed of braking directly varied to the braking distance

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การเพิ่มการถ่ายเทความร้อนของถังน้ำร้อนในระบบผลิตน้ำร้อนที่ใช้พลังงานความร้อนทิ้งจากเครื่องปรับอากาศ
การเพิ่มการถ่ายเทความร้อนของถังน้ำร้อนในระบบผลิตน้ำร้อนที่ใช้พลังงานความร้อนทิ้งจากเครื่องปรับอากาศ

This research is to study in heat transfer of hot water tank from an air conditioner which is a cylinder type and has a hot water pipe around the tank. It is used for finding a position and a pattern of distribution of the hot water pipe around the tank in the highest heat transfer condition. The study uses the cylinder of hot water tank filled 45 liters of 25 oC water. An experiment separates in 3 positions of pipe wrapping which are the bottom the center and the top of the tank. Then 80 oC of hot water run thought the hot water pipe which is wrapped around the tank for 120 minutes. The result of the experiment shows that tubing position that causes the highest heat transfer is at the bottom of tank. Pipe wrapping at the bottom of the tank has the heat transfer higher than the top of the tank at 30%. Furthermore this experiment studies in spacing of hot water pipe. There are 3 types for testing which are spacing hot water pipe as one time two times and three times of diameter of pipe. The result illustrates that spacing the hot water pipe can significantly increase the heat transfer. The heat transfer of spacing the hot water pipe in three times of diameter of pipe is higher 5.8 % than spacing in one times. In addition this research is to study in the effect of turbulent flow on the heat transfer by installing agitator in order to stir water in the tank. The result is that water stirring in the tank for increasing the heat transfer is not effective for investment because the energy using for stirring is higher than the enhanced heat transfer

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จุดหลอมเหลวและสัมประสิทธิ์การพาความร้อนแบบธรรมชาติของขี้ผึ้งพาราฟิน
จุดหลอมเหลวและสัมประสิทธิ์การพาความร้อนแบบธรรมชาติของขี้ผึ้งพาราฟิน

This research was aimed to study melting behavior of paraffin wax and to evaluate the natural heat convection coefficient of solid cylinder paraffin wax. Two grades of solid paraffin wax; white commercial grade and yellow market grade were studied. Three sizes of flat test tube in diameter 1.5 2.0 and 2.5 centimeters were used. Three different amounts of paraffin indicated from samples’ heights of 5 7 and 10 centimeters were set. The results found the average melting point of both grade paraffin ranged from 44-77 oC. Based on the numerical analysis heat behavior of solid cylinder paraffin at the initial temperature of 50 oC to room temperature of about 30 oC found that natural convection coefficients was ranged from 3 to 9 W/m 2oC. Melting point temperature was found mass independent property while natural convection coefficient declined as the sample’s diameter size inclined

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การศึกษาพฤติกรรมการถ่ายเทความร้อนของจานเบรกด้วยระเบียบวิธีไฟไนต์เอลิเมนต์
การศึกษาพฤติกรรมการถ่ายเทความร้อนของจานเบรกด้วยระเบียบวิธีไฟไนต์เอลิเมนต์

Admittedly a disc brake plays an important role in the auto part industry since it concerns directly with safety. Therefore the wide range of disc brake has been designed in order to develop its heat ventilation. There are two physical kinds of brakes: front-vented disc brake and backvented disc brake. As a result such difference affects directly to the heat ventilation which is a vital factor of the brake’s capability. The project team recognizes its importance and tries to create the test to find out the temperature diffusion of the disc brake with the hope to evaluate the coefficient of the heat convection varied by the temperature changing in both kinds of brakes under the forced heat convection in the steady condition. However the steady heat conduction and radiation value will not be counted because it is insignificant. The JASO C406: 2000 Standard is adopted as a guideline in the test. The outcome coefficient of heat conduction will be used in the simulation via the Finite Element Method (FEM) in order to study the temperature diffusion and heat ventilation of both kinds of brakes at each temperature level. Consequently the experimental work reveals then the heat convection coefficients of both kinds are unidirectional. The heat convection coefficient of the front-vented disc brake is 4.40 % in average higher than that of the back-vented disc brake. From the simulation the front-vented disc brake can ventilate the heat better than the back-vented disc brake at 3.02 % in average. It can be summarized that the front-vented disc brake has more temperature difference than the backvented disc brake. Hence the front-vented disc brake likely gets more stress from the temperature than the back-vented disc brake and might be damaged during the operation more than the another type.

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