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Expander Operated Gas Processing April, 2015
L’
Expander Operated Gas Processing:
Cooler NGL (Natural Gas Liquid) temperatures and maximized
uptime with Helidyne’s NGL Expander design.
Author:
Joseph James
Mechanical Engineer
April, 2015
Specifications:
Flowrates 1-10 mmscfd
Max. Pressure 1440 psi
Min. Temperature -50 °F
Power Generation up to 50 kW
Expander Operated Gas Processing April, 2015
Table of Contents
Executive Summary 1
Introduction 2
JT Skid Configuration 3
JT/MRU Skid Configuration 4
Expander Skid Configuration 5
How It Works 6
Empirical Data 8
Mathematical Validation 11
Package Design 13
Contact Us 14
Expander Operated Gas Processing April, 2015
pg. 1
Executive Summary:
Recent advancements in fracking and remote well operations have proven to be a very effective
method to stimulate wells and increase production. Unfortunately, infrastructure development is either
not feasible or delayed years to service remote wells making gaseous product transportation an
economic impossibility. Consequently, remote well and NGL processing equipment are the only viable
means of keeping production numbers high. Liquefying as much of the wellhead gas as possible makes
trucking transports possible, however, this creates challenges when trying to maximize wellhead gas
recovery. Despite all efforts, over 150 million cubic feet of natural gas is flared each day in remote areas
of North Dakota.
Helidyne’s NGL drop-out package offers a solution that minimizes gas flaring, reduces
downtime, and generates electricity as a bi-product. Wellhead gas is typically cooled through a high-
pressure / JT cooling system. This cooling process condenses the “heavy” gasses into a liquid making
remote truck transport economical. The system outlet temperature dictates the amount of heavy liquids
recovered; lower temperatures produce more NGLs. Depending on wellhead gas composition, these
“JT” skids have the capability of reaching temperatures of -30 °F. Since the Helidyne expander extracts
energy from the high pressure fluid in addition to utilizing the JT effect, it will always produce a colder
exhaust temperature than any JT valve. This results in more liquid recovery and higher revenue for the
customer. On average, the Helidyne expander will produce a 10-30 °F colder exhaust temperature than
a JT valve. This document illustrates a few configurations used within the industry, empirical data of the
Helidyne expander, and how the Helidyne NGL drop-out package is different.
Helidyne’s Model 4400 Expander
Figure 1
Expander Operated Gas Processing April, 2015
pg. 2
Introduction:
Wellhead gas is always a byproduct of oil production and needs to be separated. The flowrate of
separated gas varies from well-to-well with the most common wells producing about 3-5 mmscfd of gas.
This separated gas contains rich components like propane and butanes with a methane mol % ranging
from 40% (wetter gas) to 80% (dryer gas). Because these sites are in remote locations, typically no
infrastructure (including grid power) is present to transport the gas. Shipping the gas via freight isn’t
economical as the transport cost per cubic foot is unreasonable. However, liquefying these gases
reduces the volume making transport profitable.
There are several approaches to liquefying
NGLs. The most common method is by a heat
exchanger coupled with a JT skid. In this scenario, the
wellhead gas is compressed from 30-40 psi up to 1000
psi. The temperature of the gas is increased to 100-
150 °F at this high pressure. It then goes through a
heat exchanger that lowers the temperature to 20-50
°F while keeping it at that high pressure (some of the
heavy gases liquefy at this stage and drop out). The gas is then fed through a JT valve which uses the
Joule Thompson effect to lower the fluid temperature as it passes from a high-to-low pressure system.
This JT valve typically drops the pressure down to 100-400 psi and cools the gas in the range of -30 to -
10 °F. Heavy gases liquefy and are extracted from the main gas stream. The desired end product is a gas
with high methane content (typically between 80% and 90% methane).
Occasionally, if the wellhead gas is
extremely rich (40%-60% methane), a MRU
(mechanical refrigeration unit) will be installed
with a JT valve to cool the gas further. Rich gasses
have a smaller change in temperature when only
utilizing the JT effect thus requiring additional
cooling from an MRU to liquefy gas. These
refrigeration units also require an on-site
generator and consume approximately 125 kW.
Adding an MRU to a gas processing site is an
expensive proposition. It requires a leased MRU,
rented gas-powered generator, and on-going
maintenance as this equipment has proven to be unreliable mechanically and functionally not suited for
North Dakota’s rich gas and extreme environment. The Helidyne expander package replaces the JT valve
and removes the need for an MRU for rich gas wellheads. By having the capability of extracting fluid
energy from the gas stream, resultant temperatures are between 10 and 30 °F lower than a JT valve, and
comparable to a JT+MRU system. But, unlike the MRU, the Helidyne expander generates power instead
of consuming it; removing any need for an on-site generator and the MRU itself.
A Helidyne Expander
will produce lower NGL
temperatures than any
JT valve. Always.
A Helidyne expander is a
self-starting, fully
automated, mechanical
device that utilizes only
one electric motor.
Expander Operated Gas Processing April, 2015
pg. 3
Below are two of the most common NGL drop-out skid configurations. The first diagram (figure
2) shows a JT skid configuration, which is typically used for a leaner wellhead gas (70% methane content
or higher). The second diagram (figure 3) shows the typical configuration for a wellhead that provides a
rich gas (Methane content as low as 40%). Richer gases have steeper “p vs h” charts (see page 7), which
renders the JT effect less efficient; thus requiring additional cooling from a generator-powered
refrigeration unit.
State Pressure Temperature Flow Description
1 30 to 40 psi 50 to70 °F Rich wellhead gas (methane content between 40% and 80%)
2 1000 psi 100 to 150 °F Hot, high pressure wellhead gas
3 1000 psi 30 to 60 °F Cooled, high pressure wellhead gas/liquid mixture
4 150 psi 30 to 60 °F Dropped out liquids collected from tank #1
5 1000 psi 30 to 60 °F Cooled, high pressure wellhead gas (higher methane content then states 1-3)
6 150 psi -30 to 0 °F Cold, low pressure gas/liquid mixture
7 150 psi -30 to 0 °F Dropped out liquids collected from tank #2
8 150 psi -30 to 0 °F Cold, low pressure gas (>80% methane content), used for heat exchanger
9 150 psi 30 to 70 °F Cooled, low pressure “lean” gas sent for processing
Reciprocating
Compressor
NGL
Collection
Tank
Separator
Tank #1
Separator
Tank #2
JT Throttling
Valve
Shell and Tube
Heat Exchanger
1
2
3
5
4
6
8
7
9
JT Skid Configuration (Typically used for leaner wellhead
gas applications, methane > 70%)
Figure 2
Expander Operated Gas Processing April, 2015
pg. 4
JT/MRU Skid Configuration
(Typically used for rich wellhead
gas applications, methane < 70%)
State Pressure Temperature Flow Description
1 30 to 40 psi 50 to70 °F Rich wellhead gas (methane content between 40% and 80%)
2 1000 psi 100 to 150 °F Hot, high pressure wellhead gas
3 1000 psi 30 to 60 °F Cooled, high pressure wellhead gas/liquid mixture
4 150 psi 30 to 60 °F Dropped out liquids collected from tank #1
5 1000 psi 30 to 60 °F Cooled, high pressure wellhead gas (higher methane content than states 1-3)
6 150 psi -30 to 0 °F Cold, low pressure gas/liquid mixture
7 150 psi -30 to 0 °F Dropped out liquids collected from tank #2
8 150 psi -30 to 0 °F Cold, low pressure gas( higher methane content then states 1-6)
9 150 psi -50 to -20 °F Extra cold, low pressure gas/liquid mixture
10 150 psi -50 to -20 °F Dropped out liquids from tank #3
11 150 psi -50 to -20 °F Extra cold, low pressure gas used for heat exchanger (>80% methane content)
12 150 psi 10 to 70 °F Cooled, low pressure “lean” gas sent for processing
NGL
Collection
Tank
Separator
Tank #1
Separator
Tank #2
Separator
Tank #3
JT Throttling
Valve
Shell and Tube
Heat Exchanger Reciprocating
Compressor
Mobile Refrigeration Unit
(MRU)
125 kW
Generator
1
2
3
5 6
4
7
8
9
11
12
10
Figure 3
Expander Operated Gas Processing April, 2015
pg. 5
Below is the configuration for a Helidyne expander NGL drop-out skid. As shown in the tables,
using a Helidyne expander combines the simplicity of a JT configuration, while producing the cold
temperatures of a JT+MRU Skid. The Helidyne expander is a mechanical device (with self-cleaning
rotors) that only utilizes one electric motor (oil pump). This translates to 1000’s of hours of runtime
without maintenance. As previously mentioned, the bi-product of using a Helidyne expander is available
shaft power capable of producing up to 50 kW of electricity. This can be used to operate a control room,
run climate control for operators, power heating equipment to
prevent potential system freezes, or drive any auxiliary device.
State Pressure Temperature Flow Description
1 30 to 40 psi 50 to70 °F Rich wellhead gas (methane content between 40% and 80%)
2 1000 psi 100 to 150 °F Hot, high pressure wellhead gas
3 1000 psi 30 to 60 °F Cooled, high pressure wellhead gas/liquid mixture
4 150 psi 30 to 60 °F Dropped out liquids collected from tank #1
5 1000 psi 30 to 60 °F Cooled, high pressure wellhead gas (higher methane content then states 1-3)
6 150 psi -50 to -20 °F Cold, low pressure gas/liquid mixture
7 150 psi -50 to -20 °F Dropped out liquids collected from tank #2
8 150 psi -50 to -20 °F Cold, low pressure gas (>80% methane content), used for heat exchanger
9 150 psi 10 to 70 °F Cooled, low pressure “lean” gas sent for processing
Expander Skid
Configuration (Applications include both
dry and wet gas wells)
Reciprocating
Compressor
Shell and Tube
Heat Exchanger
Separator
Tank #1 Separator
Tank #2
NGL
Collection
Tank
Helidyne Expander
1
2
3
4
5
6
7
8
9
9
Up to 50 kW of
available shaft power.
Figure 4
Expander Operated Gas Processing April, 2015
pg. 6
How It Works: The Helidyne expander is a positive displacement, planetary rotor
design. In other words, the volume ratio from inlet-to-exhaust is 1:1 and can be
assumed to behave like a hydraulic motor (for incompressible flows only, Mach
< .3). Rotors (3 or 4 rotor configuration) are designed with a helical twist that
mesh with adjacent rotors when assembled together. As the rotors rotate in the
same direction they form a progressive working cavity within the rotor mesh.
Each revolution produces two or three cycles for a 4 or 3 rotor configuration
respectively. Figure 7 illustrates the shape of the volume within the 4 rotor
machine.
During operation, the inlet of the machine is always open to the gas
source, thus maintaining a constant fluid density. After turning half a rotation,
the inlet closes completely, enclosing the gas in the cavity. After which, the
rotors open on the backside exhausting the gas. As the leading volume of gas is
being exhausted, a new volume of gas is entering on the frontend creating 2
power cycles per revolution.
Shaft power produced by the expander is calculated using the hydraulic
power equation (due to the 1:1 ratio):
𝑃𝑠ℎ𝑎𝑓𝑡 = ∆𝑝�̇�𝐴𝑐𝑡𝑢𝑎𝑙 𝑅𝑜𝑡𝑜𝑟𝐸𝑣𝑜𝑙 1
Where: 𝑃𝑠ℎ𝑎𝑓𝑡 = 𝑆ℎ𝑎𝑓𝑡 𝑝𝑜𝑤𝑒𝑟
∆𝑝 = 𝑃𝑟𝑒𝑠𝑠𝑢𝑟𝑒 𝑎𝑐𝑟𝑜𝑠𝑠 𝑡ℎ𝑒 𝑟𝑜𝑡𝑜𝑟𝑠 �̇�𝐴𝑐𝑡𝑢𝑎𝑙 𝑅𝑜𝑡𝑜𝑟 = "actual" flow rate 𝑡ℎ𝑟𝑜𝑢𝑔ℎ 𝑡ℎ𝑒 𝑟𝑜𝑡𝑜𝑟𝑠 𝐸𝑣𝑜𝑙 = 𝐸𝑥𝑝𝑎𝑛𝑑𝑒𝑟 𝑉𝑜𝑙𝑢𝑚𝑒𝑡𝑟𝑖𝑐 𝐸𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦
The power produced from the expander is the byproduct of using it in
an NGL application, not the objective. Gas cooling is the primary goal and
should be maximized. As per its definition, an expander captures energy within
a fluid by having it perform work on a mechanical device (usually a rotor or a
blade). This reduces the enthalpy (internal energy plus the product of volume
and pressure), which reduces the heat content of the fluid. JT valves use the Joule Thompson effect
which is an isenthalpic process (enthalpy remains constant) where total energy is conserved in adiabatic
gas expansion (no heat exchanged, no work performed). This process causes an increase in potential
energy but a decrease in kinetic energy (decrease in temperature) but total energy is conserved. In an
expander, on the other hand, gas performs positive work during expansion which reduces its enthalpy
(reducing total energy) thus cooling the gas more than a JT valve.
Gas “Packet”
Rotors at full torque position
(half cycle or quarter turn)
Shape of a gas volume
passing through the Expander
Figure 5
Figure 7
Rotors at starting position
(beginning of a cycle)
Figure 6
Expander Operated Gas Processing April, 2015
pg. 7
Each fluid composition has a spectrum of cooling capability called the isentropic range.
Removing all the potential energy from a fluid stream would be an “ideal isentropic process” (or in other
words, a system with 100% efficiency). Depending on expander efficiency, the enthalpy removed will lie
somewhere between its isentropic and isenthalpic temperatures.
A Mollier chart (Figure 8), which graphs pressure versus enthalpy, illustrates this concept
further. A brief explanation of this chart is beneficial. This specific Mollier chart uses methane as the
fluid; the green lines indicate isothermal processes, black lines are isentropic processes, and the brown
line is the saturated-state bell curve. The black dot is the initial state of this particular example (1000 psi
@ 30 °F). The red line shows the cooling process of an isenthalpic process (or JT process). Since an
expander removes energy, the reduced enthalpy lowers the temperature further as shown by the purple
line. The theoretical maximum cooling for this example, without an external heat pump, is shown by the
blue line. Notice all three scenarios have the same exhaust pressure (150 psi) but different
temperatures.
The change in enthalpy is calculated by:
∆ℎ = 𝔑𝑖𝑛𝑍𝑖𝑛𝑇𝑖𝑛𝐸𝑣𝑜𝑙 (1 −𝑝𝑜𝑢𝑡
𝑝𝑖𝑛) 2
Where: ∆ℎ = 𝐶ℎ𝑎𝑛𝑔𝑒 𝑖𝑛 𝑒𝑛𝑡ℎ𝑎𝑙𝑝𝑦 𝔑𝑖𝑛 = 𝑅𝑒𝑎𝑙 𝑔𝑎𝑠 𝑐𝑜𝑛𝑠𝑡𝑎𝑛𝑡 𝑍𝑖𝑛 = 𝑇ℎ𝑒 𝑐𝑜𝑚𝑝𝑟𝑒𝑠𝑠𝑖𝑏𝑖𝑙𝑖𝑡𝑦 𝑓𝑎𝑐𝑡𝑜𝑟 𝑎𝑡 𝑡ℎ𝑒 𝑒𝑥𝑝𝑎𝑛𝑑𝑒𝑟 𝑖𝑛𝑙𝑒𝑡 𝑝𝑖𝑛 = 𝐸𝑥𝑝𝑎𝑛𝑑𝑒𝑟 𝑖𝑛𝑙𝑒𝑡 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 𝑝𝑜𝑢𝑡 = 𝐸𝑥𝑝𝑎𝑛𝑑𝑒𝑟 𝑜𝑢𝑡𝑙𝑒𝑡 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 𝑇𝑖𝑛 = 𝐸𝑥𝑝𝑎𝑛𝑑𝑒𝑟 𝑖𝑛𝑙𝑒𝑡 𝑇𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒 𝐸𝑣𝑜𝑙 = 𝐸𝑥𝑝𝑎𝑛𝑑𝑒𝑟 𝑣𝑜𝑙𝑢𝑚𝑒𝑡𝑟𝑖𝑐 𝑒𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦
Figure 8
Expander Operated Gas Processing April, 2015
pg. 8
Which is derived from the conservation of energy:
𝑃𝑠ℎ𝑎𝑓𝑡 = �̇�∆ℎ 3
Where: �̇� = 𝐸𝑥𝑝𝑎𝑛𝑑𝑒𝑟 𝑖𝑛𝑙𝑒𝑡 𝑚𝑎𝑠𝑠 𝑓𝑙𝑜𝑤𝑟𝑎𝑡𝑒
Equation 2 demonstrates a higher pressure ratio and greater expander efficiency will yield lower
temperatures. Or, in terms of the above Mollier Chart (figure 8), the greater the pressure ratio and
expander efficiency, the closer the purple line moves toward the blue line and higher isentropic
efficiency. Current Helidyne expander volumetric efficiencies are approximately 20-40% (depending on
the application). As machining processes become more advanced, leakage within the expander system
will be reduced which will increase volumetric efficiency resulting in lower exhaust temperatures.
The Helidyne expander has a unique design that allows it to be the only expander on the market
suitable for the harsh conditions experienced in a total-flow NGL application. The current rotor design
for Model 4400 allows for pressure drops of up to 1440 psi, flows up to 10 mmscfd, and power
generation up to 50 kW. However, the most important capability of the Helidyne expander is its ability
to process 2-phase expansion and be self-cleaning. This quality alone makes the Helidyne expander a
more effective and reliable option over other expander types.
Empirical Data:
The Helidyne expander has been tested using air, nitrogen, and pipeline natural gas to validate
the above mathematical models. Helidyne’s test site is located in St. George, Utah at the Red Rock
Generation Facility and includes a 1300 HP natural gas fueled compressor, PLC operated control room,
and a piping infrastructure to run various tests (see figure 9). This test site is capable of producing a flow
of 6 mmscfd at 1000 psi using pipeline natural gas or nitrogen (tests using air performed at a different
location).
The Helidyne Red Rock Test Site located in St. George, Utah
Figure 9
Expander Operated Gas Processing April, 2015
pg. 9
Several 24 hour tests were completed using pipeline quality natural gas. These tests were
designed to measure various system performances including pressure/flow variance, stability, and
exhaust cooling. The power produced was controlled using a flow control valve upstream that regulated
the pressure to the expander. “System Pressure” is the line pressure upstream of the control valve,
“expander inlet pressure” is the line pressure between the flow control valve and the expander (and is
the pressure used to compare with a JT process), and the “exhaust pressure” is the line pressure after
the expander.
Figure 10 illustrates results of the first half of a 24 hour test. The first graph displays the
expander having a varying system pressure (dark blue line, ranging from 450 to 850 psi) while
maintaining a constant 15 kW power output (teal line). In addition to testing system stability, this
provided different system temperatures that varied with system pressure.
The second graph shows the temperatures of the system before the flow control valve (red line),
the temperatures right before the expander (the purple line), and the exhaust gas temperatures (green
line). A set of data points (indicated by the red line) are displayed below the temperature graph. These
values will be used to compare the performance of the Helidyne expander versus a JT valve.
Time Stamp 10/20/2014 18:00
System Pressure 557.80 psi
Expander Inlet Pressure 350.08 psi
Exhaust Pressure 49.30 psi
System Temperature 92.6 °F
Inlet Temperature 82.3 °F
Exhaust Temperature 53.1 °F
Power 14.94 kW
Figure 10
Expander Operated Gas Processing April, 2015
pg. 10
The numbers in the table of figure 10 can be reproduced using NIST (National Institute of
Standards and Technology) data and also give the exhaust temperature of a JT valve under the same
application (see figure 11). This validates equations 1-3 (note: pressures are absolute):
Line 1 = System State
Line 2 = Expander Inlet State
Line 3 = Rotor Inlet
Line 4 = Expander Exhaust
Line 6 = JT Temperature
Drop (for comparison)
As figure 11 shows, the Helidyne expander has a 13 degree cooler temperature than a similar
test with a JT valve. This is because the expander extracts fluid energy from the flow and converts it to
mechanical work. As equation 2 shows, a greater pressure ratio will yield a greater change in enthalpy,
which translates to cooler temperatures. The above test had a 300 psi drop across the expander (as per
the 15 kW protocol requirement). If a greater
power was desired, the pressure drop across
the expander could be raised to the available
500 psi drop and the exhaust gas would be a
lower temperature than line 4 of figure 11.
It is important to note that exhaust
temperatures will vary depending on fluid
composition, pressure drop, initial temperature,
ambient temperature, and flowrate (affects
expander volumetric efficiency). The Mollier
chart in figure 8 shows methane (at certain
points, pressures, and temperatures) displaying
very curvy isothermal lines. In other words,
methane promotes very good cooling when dropping from warmer, higher to lower pressures. However,
when the fluid composition changes by reducing the methane mol percentage, the isothermal lines
become much steeper, similar to the left-hand side of figure 8’s methane chart. In short, lower mol
percentage methane composition makes JT cooling less effective for wellhead gas. Each well will have its
own fluid composition, flow, temperature, and pressures that will produce unique results when using a
Helidyne expander.
Isenthalpic Process
The Helidyne Expander’s
versatile profile includes
flows from 1-10 mmscfd,
pressures up to 1440 psi,
and temperatures down
to -50 °F.
Figure 11
Expander Operated Gas Processing April, 2015
pg. 11
Mathematical Validation:
𝑃𝑠ℎ𝑎𝑓𝑡 = �̇�∆ℎ
14.94 𝑘𝑊 + 4.8 𝑘𝑊 (𝑃𝑎𝑟𝑎𝑠𝑖𝑡𝑖𝑐 𝐿𝑜𝑠𝑠𝑒𝑠) = 19.74 𝑘𝑊 = �̇� ∙ 16.12𝑘𝐽
𝑘𝑔
�̇� =19.74
𝑘𝐽𝑘𝑔
16.12𝑘𝐽𝑠
�̇� = 1.225 𝑘𝑔
𝑠
�̇� = 𝜌�̇�𝐴𝑐𝑡𝑢𝑎𝑙
𝑊ℎ𝑒𝑟𝑒:
𝜌 = 𝐹𝑙𝑢𝑖𝑑 𝐷𝑒𝑛𝑠𝑖𝑡𝑦
�̇�𝐴𝑐𝑡𝑢𝑎𝑙 =�̇�
𝜌
�̇�𝐴𝑐𝑡𝑢𝑎𝑙 𝐸𝑥𝑝𝑎𝑛𝑑𝑒𝑟 𝐼𝑛𝑙𝑒𝑡 =1.225
𝑘𝑔𝑠
16.727𝑘𝑔𝑚3
�̇�𝐴𝑐𝑡𝑢𝑎𝑙 𝐸𝑥𝑝𝑎𝑛𝑑𝑒𝑟 𝐼𝑛𝑙𝑒𝑡 = .073𝑚3
𝑠
Converting to standard flowrate:
�̇�𝑠𝑡𝑑 =�̇�𝑎𝑐𝑡𝑢𝑎𝑙 (
𝑝𝑎𝑐𝑡𝑝𝑠𝑡𝑑
) (𝑇𝑠𝑡𝑑𝑇𝑎𝑐𝑡
)
𝑍𝑖𝑛
�̇�𝑠𝑡𝑑 =
. 073𝑚3
𝑠 (363.08
𝑙𝑏𝑠𝑖𝑛2
13𝑙𝑏𝑠𝑖𝑛2
) (519.7°𝑅542.0°𝑅
)
. 96 = 2.036
𝑚3
𝑠
Calculating equation 1:
𝑃𝑠ℎ𝑎𝑓𝑡 = ∆𝑝�̇�𝐴𝑐𝑡𝑢𝑎𝑙𝐸𝑣𝑜𝑙
∆𝑝 = [300.78𝑙𝑏𝑠
𝑖𝑛2− 125
𝑙𝑏𝑠
𝑖𝑛2(𝑐𝑎𝑙𝑐𝑢𝑙𝑎𝑡𝑒𝑑 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 𝑑𝑟𝑜𝑝 𝑡ℎ𝑟𝑜𝑢𝑔ℎ 𝑡ℎ𝑒 𝑚𝑎𝑛𝑖𝑓𝑜𝑙𝑑)] = 1,211,958.2
𝑁
𝑚2
Converting Standard back into actual:
�̇�𝐴𝑐𝑡𝑢𝑎𝑙 =�̇�𝑠𝑡𝑑𝑍𝑖𝑛
(𝑝𝑎𝑐𝑡𝑝𝑠𝑡𝑑
) (𝑇𝑠𝑡𝑑𝑇𝑎𝑐𝑡
)
Expander Operated Gas Processing April, 2015
pg. 12
�̇�𝐴𝑐𝑡𝑢𝑎𝑙 𝑅𝑜𝑡𝑜𝑟 =1.7742
𝑚3
𝑠(. 97)
(238.08
𝑙𝑏𝑠𝑖𝑛2
13𝑙𝑏𝑠𝑖𝑛2
) (519.7°𝑅535.4°𝑅
)
= .097𝑚3
𝑠
Calculating Volumetric Efficiency:
𝐸𝑣𝑜𝑙 =�̇�𝐶𝑎𝑣𝑖𝑡𝑦
�̇�𝐴𝑐𝑡𝑢𝑎𝑙 𝑅𝑜𝑡𝑜𝑟
Where:
�̇�𝐶𝑎𝑣𝑖𝑡𝑦 = 𝐺𝑒𝑜𝑚𝑒𝑡𝑟𝑖𝑐 𝑐𝑎𝑣𝑖𝑡𝑦 𝑓𝑙𝑜𝑤𝑟𝑎𝑡𝑒 𝑜𝑓 𝑡ℎ𝑒 𝑟𝑜𝑡𝑜𝑟𝑠 = .0166𝑚3
𝑠 𝑓𝑜𝑟 𝑡ℎ𝑒 𝑀𝑜𝑑𝑒𝑙 4400
𝐸𝑣𝑜𝑙 =. 0166
𝑚3
𝑠
. 097𝑚3
𝑠
= .171
𝑃𝑠ℎ𝑎𝑓𝑡 = (1211958.2𝑁
𝑚2) (. 097
𝑚3
𝑠) (. 171) = 20.10 𝑘𝑊
𝑂𝑢𝑡𝑝𝑢𝑡 𝑝𝑜𝑤𝑒𝑟 = 𝐸𝐺𝑒𝑛𝑒𝑟𝑎𝑡𝑜𝑟(𝑃𝑠ℎ𝑎𝑓𝑡 − 𝑃𝑑𝑟𝑎𝑔) = .99(20.10 𝑘𝑊 − 4.8𝑘𝑊) = 15.15 𝑘𝑊 ≈ 14.94 𝑘𝑊
And finally equation 2:
∆ℎ = 𝔑𝑖𝑛𝑍𝑖𝑛𝑇𝑖𝑛𝐸𝑣𝑜𝑙 (1 −𝑝𝑜𝑢𝑡
𝑝𝑖𝑛)
∆ℎ = (. 518𝑘𝐽
𝑘𝑔 𝐾) (. 97)(297 𝐾)(. 171) (1 −
62.3𝑙𝑏𝑠𝑖𝑛2
238.08𝑙𝑏𝑠𝑖𝑛2
) = 18.8𝑘𝐽
𝑘𝑔
And comparing equation 2 results to empirical data from the NIST Chart in figure 11:
893.15𝑘𝐽
𝑘𝑔− 877.03
𝑘𝐽
𝑘𝑔= 16.12
𝑘𝐽
𝑘𝑔 ≈ 18.8
𝑘𝐽
𝑘𝑔
These empirically validated mathematical models allow for any natural gas composition to be
calculated. If given the inlet pressure, outlet pressure, and inlet temperature; the power produced and
change in enthalpy can be predicted. As stated previously, a Helidyne expander will always produce
lower temperatures than a JT valve and comparable temperatures as an MRU configuration with the bi-
product being usable shaft power.
NOTE: Thermodynamic calculations will have a greater margin of error than power calculations due to the inherent approximations in thermodynamic modeling.
Expander Operated Gas Processing April, 2015
pg. 13
Package Design:
Insulated NGL Collection Tanks
Model 4400 Helidyne Expander
Onboard PLC/HMI
Skid Connections Insulated Heat Exchanger
Generator (Or any device
requiring shaft power)
Onboard Battery System
Expander Operated Gas Processing April, 2015
pg. 14
Contact Us:
Address: 1425 Redledge Rd. Suite 102
Washington, Utah 84780
Office Phone: 435-627-1805
Email: sales@helidynepower.com
For More Information about our products and
services, please visit our website:
www.HelidynePower.com
© Helidyne LLC 2015. All rights reserved. No part of this document or its contents may be reproduced, republished, publicly
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contained in this document is subject to change without notice and is provided on an “as-is” basis. Helidyne LLC. Disclaims all
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particular purpose, except as provided by written agreement.
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