Part Of A Processing Plant Consists Of A Pipeline Which Carr

Part Of A Processing Plant Consists Of a Pipeline Which Carries a Chem

Part of a processing plant consists of a pipeline which carries a chemical with a relative density (to water) of 0.7. The pipeline is circular in section with a diameter which changes from 200mm at inlet to 150mm at outlet. The outlet of the pipe is 12m above that of the inlet. The pipeline is required to carry a mass flow rate of the chemical of 100kgs-1, and the pressure at the pipeline outlet must be 2bar. a) Determine the volumetric flow rate of the chemical b) Determine the velocity of the chemical at the pipeline inlet and its outlet. c) Determine the pressure required at the pipeline inlet, in bar, to achieve the desired pressure at the outlet (2 bar) I am new to this so please show all working if possible to help me better understand the process. Thank you in advance.

Paper For Above instruction

Introduction

The calculation of flow characteristics within pipelines carrying fluids, particularly chemicals, is fundamental in process engineering. This paper addresses the problem of determining the volumetric flow rate, velocities at different points, and the inlet pressure required to maintain specified outlet conditions for a chemical being transported through a pipeline with varying diameters and elevation. We will systematically approach the problem through fluid mechanics principles including the continuity equation, Bernoulli’s equation, and pressure head calculations.

Problem Data and Parameters

The fluid (chemical) has a relative density (RD) of 0.7, implying its density (\(\rho\)) is \(0.7 \times 1000\, \text{kg/m}^3 = 700\, \text{kg/m}^3\). The inlet diameter (\(D_1\)) is 200 mm or 0.2 m, and the outlet diameter (\(D_2\)) is 150 mm or 0.15 m. The elevation difference (\(\Delta z\)) is 12 m, with the outlet 12 m above the inlet. The mass flow rate (\( \dot{m} \)) is 100 kg/s. The required outlet pressure (\(P_2\)) is 2 bar, which corresponds to a gauge pressure considering atmospheric conditions.

Part A: Volumetric Flow Rate (\(Q\))

The volumetric flow rate, \(Q\), relates to mass flow rate as:

\[

Q = \frac{\dot{m}}{\rho}

\]

Substituting known values:

\[

Q = \frac{100\, \text{kg/s}}{700\, \text{kg/m}^3} \approx 0.14286\, \text{m}^3/\text{s}

\]

Thus, the volumetric flow rate of the chemical is approximately 0.143 m³/s.

Part B: Velocities at Inlet and Outlet

Using the cross-sectional area \(A = \frac{\pi}{4} D^2\), velocities (\(v\)) are:

\[

v = \frac{Q}{A}

\]

- Inlet velocity (\(v_1\)):

\[

A_1 = \frac{\pi}{4} \times (0.2)^2 = 0.031416\, \text{m}^2

\]

\[

v_1 = \frac{0.14286}{0.031416} \approx 4.55\, \text{m/s}

\]

- Outlet velocity (\(v_2\)):

\[

A_2 = \frac{\pi}{4} \times (0.15)^2 = 0.017671\, \text{m}^2

\]

\[

v_2 = \frac{0.14286}{0.017671} \approx 8.08\, \text{m/s}

\]

The chemical velocity increases as the pipe narrows from inlet to outlet.

Part C: Inlet Pressure Calculation

Applying Bernoulli’s equation between inlet and outlet, accounting for elevation difference, pressure, and velocity changes:

\[

P_1 + \frac{1}{2} \rho v_1^2 + \rho g z_1 = P_2 + \frac{1}{2} \rho v_2^2 + \rho g z_2

\]

Rearranged to solve for \(P_1\):

\[

P_1 = P_2 + \frac{1}{2} \rho (v_2^2 - v_1^2) + \rho g (z_2 - z_1)

\]

Convert \(P_2\) from bar to Pascals:

\[

P_2 = 2\, \text{bar} = 200,000\, \text{Pa}

\]

Using \(g = 9.81\, \text{m/s}^2\), and \(\Delta z = 12\, \text{m}\):

\[

P_1 = 200,000 + \frac{1}{2} \times 700 \times (8.08^2 - 4.55^2) + 700 \times 9.81 \times (-12)

\]

Calculate each term:

- Kinetic energy difference:

\[

\frac{1}{2} \times 700 \times (65.3 - 20.7) = 350 \times 44.6 \approx 15,610\, \text{Pa}

\]

- Potential energy term:

\[

700 \times 9.81 \times (-12) = -82,494\, \text{Pa}

\]

Then:

\[

P_1 = 200,000 + 15,610 - 82,494 = 133,116\, \text{Pa}

\]

Convert back to bar:

\[

P_1 \approx 1.33\, \text{bar}

\]

Result: The inlet pressure must be approximately 1.33 bar (gauge or absolute, depending on context) to achieve the desired outlet pressure.

Discussion and Conclusion

The flow analysis illustrates the application of fundamental fluid mechanics principles to practical pipeline problems. The volumetric flow rate remains constant along the pipeline, confirmed through the continuity equation. The increased velocity at the outlet due to narrowing pipe diameter leads to higher kinetic energy, which must be supplied via suitable inlet pressure. The significant elevation difference demands additional pressure head, highlighting the importance of pumps and pressure control mechanisms in pipeline design.

Understanding these relationships enables engineers to design efficient piping systems that meet operational criteria while maintaining safety and cost-effectiveness.

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