How to find velocity of gas pump flowing into car tank

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Discussion Overview

The discussion revolves around determining the velocity of gasoline being pumped into a car tank. Participants explore various factors that may influence this calculation, including mass flow rate, cross-sectional area, and potential considerations like atmospheric and vapor pressures. The scope includes theoretical and practical aspects of fluid dynamics as applied to fuel pumping.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • One participant presents a general balance equation for fluid flow but expresses uncertainty about the relevance of atmospheric pressure and vapor pressure in their calculations.
  • Another participant suggests starting with water to simplify the problem and asks for clarification on the specific information needed regarding pump pressure and flow rate.
  • Several participants emphasize the need for a clear equation to calculate the velocity of gasoline and request definitions of terms used in the initial post.
  • One participant proposes measuring the volume flow rate and dividing it by the cross-sectional area of the hose to find the velocity, while questioning the necessity of high accuracy for the calculations.
  • Another participant outlines a practical method for measuring flow rate using a stopwatch and the pump's display, but notes the original poster has not engaged in the discussion for over two years.

Areas of Agreement / Disagreement

The discussion does not reach a consensus, as participants express various approaches and considerations without settling on a single method or equation for calculating the velocity of gasoline being pumped.

Contextual Notes

Participants highlight the importance of defining terms and the potential impact of different factors, such as vapor pressure, but do not resolve these uncertainties or assumptions. The discussion also reflects a lack of recent engagement from the original poster.

Who May Find This Useful

This discussion may be of interest to individuals studying fluid dynamics, those involved in engineering or physics, and anyone seeking practical methods for measuring flow rates in fuel systems.

medale14
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TL;DR
Hello, so I am stuck with the concern of making an equation that fits my standard. I'm trying to create an equation from the mass, momentum and energy balance equation according to my system. My system is a gas pump flowing into a car tank. In this to make it easier for myself I disregarded friction. I understand that to solve this equation I must use the cross-sec area of the nozzle. However, I'm stuck with how to set up the rest of the equation. Would I take inconsideration p atm?
The general balance equation is as follow: d[m{u+gz+v2/2)sys=(u+gz+v2/2)dmin-(u+gz+v2/2)dmout +dq+dw.

I understand that I would take in consideration the cross sectional area as well as the mass flow rate. However I can't figure out what else to consider as if atm pressure should be considered and vapor pressure? My main goal is to figure out the velocity if the gas being pumped into the tank.

Screenshot 2022-10-13 183213.png
 
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Let's just pump water first. Vapor pressure for gasoline might be an issue but not now. So what are you tryimg to specify?
Pump pressure required to deliver a certain flow rate? Please specify exactly what you want to know
 
I'm just trying to figure out an equation that can help me figure out the velocity for pumping gas into a car tank.
 
medale14 said:
I'm just trying to figure out an equation that can help me figure out the velocity for pumping gas into a car tank.
Can you please define all of your terms in your equation in your first post? And in the future, please try to post math in LaTeX (see the LaTeX Guide link in the Edit window). Thanks.
 
medale14 said:
I'm just trying to figure out an equation that can help me figure out the velocity for pumping gas into a car tank.

Measure the volume flow rate (gallons per minute - with a stop watch) and divide by the cross sectional area of the hose (e.g. nozzle). Or just look at the specs of petrol pumps for typical volume flow rate. What accuracy do you actually need?
I hope you wouldn't risk a DIY system for doing this sort of thing.
 
1) The pump display shows a running total of gallons delivered.
2) Use a watch with a second hand, or a stopwatch, to measure the delivery duration.
3) Divide the result from 1) above by the time from 2) above.

Note: the OP hasn't been seen since starting this thread, 2 years + 2 months ago.
 
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It seems the topic has run its course and its time to close after waiting for over 2 years for some new responses.

Thank you all for participating here. Hopefully the OP now has a car of his/her own with which to conduct this experiment and others.
 
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