Civil Engineering Hydraulics Laboratory: Analysis Of Energy Losses In Bends

Introduction

The friction between the fluid and the pipe walls and the internal friction between the fluid particles in the pipe flows is known as the energy losses. This energy losses can be caused based on the turbulence of the flow. Due to this, there is sudden contraction and enlargement that forms in the pipe. In this experiment, only the minor loss of energy occurs. They occur through the bends fittings, expansions. The purpose of this experiment is to determine the loss coefficient for the pipe flow through a range of the pipe fitting including the bends, a contraction, an enlargement, and a gate-valve. This can be done by measuring the head differences across each of several fittings connected in series and over a steady flow. This experiment is significant because it allows to be able to identify the necessary power needed for the transportation of the fluids from one point to another in the pipes. It was hypothesized that the loss coefficient will remain constant for a given fitting no matter what the flow rate of the fluid.

Materials & Methods

The Energy Losses in Bends experiment was performed as per CIV 342 Laboratory Experiment. The equipment and tools used for this experiment are the F1-22 Energy Losses in Bends and Fittings Apparatus, a stopwatch, clamps for pressure tapping connection tubes, a level, and a thermometer. For this experiment, the measure of the losses was performed differently by across the fittings only and across the gate valve only. The procedure was followed as per the laboratory manual and no changes were made to the standard test methods and materials.

Discussion

Minor losses are classified as a secondary head loss because they occur at the bends, fittings and expansions and contractions. In this experiment, the loss coefficient was determined by the values obtained by performing two different methods. These two methods of measuring the losses were through the fittings and the gate valves. For the pipe fittings, the fluid flowed through the Long bend, expansion, Short bend, Contraction, Elbow bend, Mitre bend. Based on the measured values, the head loss, flow rate, velocity, dynamic head, and loss coefficient were calculated and can be found on Table… and…According to the tables and graphs the dependence of head losses across a pipe fitting upon velocity of the fluid can be observed as the velocity is increasing so is the head loss increasing. It is justifiable to treat the loss coefficient as constant for a given fitting because its flow rate, velocity and head losses can vary. The Reynolds number of each fittings, is greater than 4000 which can be classified as a turbulent flow.

As the radius of a bens increases the fittings loss coefficient also increases because it makes the change in the velocity more abrupt. The loss coefficient of both sudden contraction and enlargement can be For the second method, the data were collected from the other group cause the device was not providing accurate measurement. The measured values for the gate valve was collected differently from how it was layout in the manual. Instead of measuring the flow as the gate valve is turned, it was performed otherwise by closing the gate valve till there is no flow. The values obtained, and the calculated values can be found in Table… Since the experiment for this section was performed otherwise, the loss coefficient for the gate valve decreases in the extent of closing the valve. It can also be observed by the calculated values that the velocity decreases as the flow rate decreases thus the loss coefficient increases. For this experiment, there were a lot of error that occurred. Some errors that can be identified as human errors.

These are due to eye reading of the pipes. The measured values could be misread, and it can affect the calculations of each result. The bench was supposed to be static so moving the bench could also affect the test results. The values of the loss coefficient may not be accurate due to that. While performing the second part of the experiment the measurement values were always the same. This was due to machine fault. Due to that we had to use other groups data.

Conclusion

This experiment was not completely successful as it did not fully meet the objectives of this lab. Based on these it can be concluded that the loss coefficient can be constant across the selected fittings although it won’t be the case for all. For further investigation, this experiment can be performed for the gate valve from opening the valve to closing it.