Catholic Health Services Differentiating and Interconverting Systems PPT Need help to differentiate and explain how to interconvert open and closed systems

Catholic Health Services Differentiating and Interconverting Systems PPT Need help to differentiate and explain how to interconvert open and closed systems in a presentation for peers.

Follow the directions to complete your slide presentation.

Follow APA (6th editon) format for the references slide and in-text citations.

Follow the directions to submit your final presentation.

Step 1. Define

Define open and closed systems.

Step 2. Classify and Explain

Classify the following as an open or closed system, and explain your classification:

Greenhouse
Circulatory system
Capped gas can
Water cycle
Sealed jar of pasta sauce
A system of your choice

Step 3. Explain

Explain how to interconvert each of the Step 2 examples to either an open or closed system. If the system is open, explain how to make it closed and vice versa.

Step 4. Suggest

Suggest additional closed systems.

Step 5. Compile

Compile your findings in a slide presentation for peers. The presentation should consist of:

– Title slide

– Eight content slides (Steps 1-3)

– References slide A preliminary study of the effect
of groundwater flow on the thermal front
created by borehole heat exchangers
…………………………………………………………………………………………………………………………………………..
Ali Tolooiyan1* and Phil Hemmingway2
1
Geotechnical and Hydrogeological Engineering Research Group (GHERG), Monash
University, Victoria, Australia; 2School of Biosystems Engineering (formerly School of Civil,
Structural and Environmental Engineering), University College Dublin, Dublin, Ireland
……………………………………………………………………………………………………………………………
Abstract
An analysis of the effects that groundwater flow has on the thermal regime created by a ground source
energy system is presented. The change in the development of the sub-surface thermal regime caused
by a groundwater flow across a site, relative to a scenario where groundwater flow does not exist,
is examined. Analysis is performed using bespoke finite-element formulations of both single- and
multi-borehole systems. The results of this work show that even a modest groundwater flow across a
site can lead to a significant change in the development of the sub-surface thermal regime.
Keywords: geothermal energy; groundwater flow; finite element; closed loop; heat transfer
*Corresponding author.
tolooiyan@gmail.com
Received 21 June 2012; revised 24 October 2012; accepted 5 November 2012
…………………………………………………………………………………………………………………………………………………………..
1 INTRODUCTION
A closed loop ground source energy (or geothermal energy)
system operates by exchanging heat with the sub-surface via a
circulating heat carrier fluid flowing around piping infrastructure which is buried in the ground. Closed loop geothermal
systems are typically categorized as either horizontal, where the
piping infrastructure is installed close to the surface in a horizontal orientation, or vertical, where the piping infrastructure
is installed in a vertical orientation. Open loop geothermal
energy systems operate by pumping water from an aquifer, exchanging heat using a heat pump and either returning water to
the aquifer or disposing it via a surface discharge system or
sewer. Open loop geothermal systems are inherently more risky
than closed loop geothermal systems; open loop geothermal
systems can require on-going maintenance throughout their operation and typically require detailed and therefore costly site
investigations (e.g. chemical analysis of waters) at the system
feasibility stage [1]. This paper deals with vertical closed loop
geothermal systems only. These systems can range in size from
single-borehole systems, which provide space heating and/or
cooling to single-family dwellings or small offices, up to large
multi-borehole installations, which may be suitable for heating
and/or cooling of large multi-storey buildings and structures.
Calculating the required quantity of sub-surface piping infrastructure required to satisfy the heating and cooling loads of
a proposed project is a critical stage in the design of a closed
loop ground-source energy system. For soils where a high
groundwater flow is present, the heat transfer process between
the heat exchanger piping and the surrounding ground may be
strongly influenced by convection effects; however, for formations with low hydraulic conductivity, the heat transfer process
is typically dominated by heat conduction [2]. Banks et al. [3]
found the phenomena of excessively high values of apparent
thermal conductivity caused by the possible presence of groundwater flow across the tested borehole heat exchanger, to exist in
3 of 26 thermal response tests carried out in the UK. This indicates that groundwater flow design problems hampering the
design of geothermal systems could be present in 10% of
cases. However, it is noted that the existence of groundwater
flow at a site is strongly related to the geology at the site and
therefore in certain regions, design issues associated with the existence of groundwater flow may be prevalent.
A number of software packages have been developed to design
and size closed loop ground source energy systems. Practically all
of these software packages being used in the ground source
energy industry (such as Energy Earth Designer [4] or GLHEPRO
[5–7]) assume heat transfer by conduction only. This paper
International Journal of Low-Carbon Technologies 2014, 9, 284– 295
# The Author 2012. Published by Oxford University Press.
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/
by-nc/3.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial
re-use, please contact journals.permissions@oup.com
doi:10.1093/ijlct/cts077 Advance Access Publication 21 December 2012
284
Effect of groundwater flow on heat exchangers
presents a preliminary investigation of the effect of groundwater
flow on the development of the thermal front created by a singleborehole heat exchanger and group of borehole heat exchangers.
The consequences of the altered shape and distribution of the
thermal front created by a ground source energy system operating
at a site effected by groundwater flow are not only important to
understand from the perspective of the individual operating
system but also important to consider the potential effect on adjacent or nearby ground source energy systems and potential future
installations on neighbouring sites. An increase in the popularity
of ground source energy systems (particularly in congested urban
areas) means that it will become increasingly important to consider the interaction between adjacent or nearby ground source
energy systems in the future [8, 9] and therefore development of
numerical and finite-element formulations capable of quantifying
the effect of groundwater flow of the sub-surface thermal regime
is required.
2 PREVIOUS WORK IN THE AREA
The following paragraphs provide an overview of previous
attempts made by researchers to understand the thermal influence imposed on a borehole heat exchanger system by groundwater flow. A large portion of the work done to date in this
area has consisted of evaluating the effect that groundwater
flow has on system efficiency (i.e. energy output) rather than
on the sub-surface thermal regime. Several models have been
constructed using TEMP/W and other softwares in order to
consider the thermal effects of conductive heat flow on geotechnical engineering structures such as dams or embankments
[10 – 14] in areas prone to permafrost.
A number of researchers have attempted to understand the
implications of groundwater flow across a borehole heat exchanger using various approaches. Claesson and Eskilson [15] constructed an ‘improved line source theory’ to describe the effect
of groundwater flow on a single-borehole heat exchanger under
steady-state conditions and concluded that the thermal effect of
natural groundwater movements homogenously spread over the
ground volume is negligible. It should be noted however that
Claesson and Eskilson [15] considered on a scenario where the
ground formation was composed of rock. The worst-case scenario therefore presented by Claesson and Eskilson [15] relates to
the effect of groundwater flow resulting from a ground formation with permeability 1026 m/s and gradient 1/66. Following
the well-known equation described by Darcy’s law (flow
velocity ¼ permeability gradient), this means that the worstcase (or highest) flow rate considered by Claesson and Eskilson
[15] is only 0.0013 m/day. The resulting findings that ‘the
thermal effect of natural groundwater movements are negligible’
are therefore not considered applicable to cases where the
geology may dictate a higher groundwater flow rate (for
example the permeability of the gravels beneath the Cork
Docklands in the South of Ireland is of the order of 5
1023 m/s [1] and therefore if a hydraulic gradient equal to or
greater than that assumed by Claesson and Eskilson [15] was
present, the resulting sub-surface thermal effects due to the
groundwater in this case would be significantly greater).
Lee and Lam [16] created a 3D finite-difference model
capable of calculating the ‘real’ thermal conductivity of a
ground formation from thermal response test field data provided by Pahud and Matthey [17] by take into account of the
thermal influence of the water flow present across the tested
borehole heat exchanger. Katsura et al. [18] present a method
for determining the velocity of groundwater flow based on the
temperature gradient observed from a thermal response test,
thermal probe test and heating well method test. Chiasson
et al. [19] found, using a 2D finite-element groundwater flow
and mass/heat transport model, that groundwater flow can
have a significant effect on borehole heat exchanger performance in cases where geological materials with high hydraulic
conductivity or fractured rocks exist.
Wang et al. [2] present a simplified numerical approach to
gain an understanding of the effect that groundwater flow has
on the thermal performance (i.e. energy output) of a borehole
heat exchanger. Comparison of results from a measurement
campaign carried out on a borehole system which was being
influenced by strong groundwater advection and the performance of the borehole system in the case of no groundwater advection (modelled using TRNSYS software [20]) indicated that
the groundwater flow provided an average performance enhancement of the borehole heat exchanger energy injection/
extraction rate of 9.8 and 12.9% during summer and winter,
respectively. The magnitude of the performance enhancement
was found to depend to a large extent on the distribution and
thickness percentage of the ground layer with the greatest
groundwater flow. Nam et al. [21] performed a similar study
by developing a simulation code capable of estimating the
effect of groundwater flow on the energy output of an energy
pile system. Fan et al. [22] reported a mathematical model and
integrated it into a previously developed integrated soil cold
storage and ground source heat pump simulation program.
They concluded that the presence of groundwater flow significantly influenced the heat transfer between the borehole heat
exchanger and the surrounding soil and therefore the energy
output of the cold storage/ground source heat pump system.
Katzenbach et al. [23] carried out finite-element model
(FEM) simulations in order to investigate the possible subsurface thermal influence on neighbouring properties caused
by the operation of a geothermal seasonal thermal storage
system in Frankfurt, Germany. Coupled conductive and convective heat transport models were created and the influence of
varying boundary conditions was investigated. The project analysed consists of 302 foundation piles with diameters of up to
1.86 m and depths of up to 27 m, of which 262 piles were
equipped with heat exchanger pipes. The project also consists
of a retaining wall of 543 piles (1.5 m diameter, up to 38 m
length) of which every second reinforced pile was equipped
with heat exchanger pipes, resulting in 130 retaining wall
energy piles. Although exact details are not provided in
International Journal of Low-Carbon Technologies 2014, 9, 284– 295 285
A. Tolooiyan and P. Hemmingway
Katzenbach et al. [23] and Katzenbach et al. [24] relating to
the ground conditions at the site, it is understood that the majority of the pile depth is surrounded by relatively impermeable
Frankfurt clay while a short, lower section of a portion of the
piles is surrounded by higher permeability Frankfurt limestone
where groundwater flow is present. It was observed that for a
constant heat extraction rate, the groundwater flow causes a reduction in the temperature drop inside and adjacent to the
borehole heat exchanger, and for a modelled flow velocity of
1 m/day results in a near-field temperature increase of 1.58C.
Katzenbach et al. conclude that the horizontal groundwater
flow results in the deflection of isotherms in the downstream
direction, resulting in a larger thermally influenced area in the
downstream direction of the energy foundation installation.
Gehlin and Hellstro?m [25] created three 2D numerical
finite difference model scenarios to investigate the short-term
influence of the thermal effects of groundwater flow in fractured rock, resulting due to single or multiple fracture zones.
Gehlin and Hellstro?m conclude that significant enhancement
of heat transfer properties is possible, even in cases where low
specific flow rates exist in fractures, and recommend further investigation of the thermal effect of groundwater flow in nonvertical fractures and fractures crossing through boreholes, the
long-term effects of fracture flow near a borehole heat exchanger and the influence of varying groundwater flow over time.
The influence of groundwater flow on thermal output of a
borehole heat exchanger was examined by Clausen [26] for a
range of flow velocities and aquifer thicknesses using a software
package called finite-element sub-surface flow and transport
simulation system [27]. The thermal performance of a borehole
heat exchanger was investigated for flow rates ranging from 0
to 5 m/day (following from Chiasson et al. [19] who suggested
typical groundwater flow rates of 4 1027 m/day in clay,
0.014–0.16 m/day in coarse sand and up to 8.4 m/day in gravel)
and a range of vertical thicknesses of fracture planes containing
horizontal flow across the borehole heat exchanger. Clausen [26]
concluded that the existence of groundwater flow across a borehole heat exchanger (which has the effect of extracting heat
from the ground unit under consideration) would lead to a significant improvement in the thermal performance of a ground
source heat pump system injecting heat into the ground.
3 FINITE-ELEMENT ANALYSIS
The purpose of the finite-element analysis described in the following sections is to gain an understanding of the development
of the sub-surface thermal front created by a borehole heat exchanger system and how it is affected by a flowing groundwater
regime. This is achieved by integrating two finite-element software packages known as TEMP/W and SEEP/W [28, 29].
TEMP/W is a finite-element software program, which has been
designed for the analysis of sub-surface thermal problems.
The software can analyse both steady-state thermal conduction
problems as well as transient problems and is typically used in
286 International Journal of Low-Carbon Technologies 2014, 9, 284– 295
industries to model freeze-thaw problems. SEEP/W is a finiteelement software program, which provides the facility to analyse
groundwater seepage and excess pore-water pressure dissipation
problems. The program allows analysis ranging from simple saturated steady-state problems to complex saturated/unsaturated
time-dependent problems. TEMP/W has the ability to integrate
with SEEP/W in order to take into account the convective heat
transfer that occurs due to flowing water. The first stage in analysing the problem at hand is to construct a TEMP/W sub-surface
heat conduction model, which is described in the next section.
3.1 TEMP/W model formation
A summary of the TEMP/W model construction and fundamental mathematical equations controlling the output of the FEM is
outlined in this paper, readers should refer to Hemmingway and
Tolooiyan [submitted for publication] and [30] for further
details. Equation (1), where F is the heat flux, l is the thermal
conductivity, T is the temperature and x is distance, shows that
heat flow due to conduction is directly dependent on the
thermal conductivity of a material and temperature gradient.
The negative sign in the equation indicates that temperature
decreases in the direction of increasing x when a positive heat
flux is imposed on a material [31]. Heat flux due to conduction
is governed by Equation (1) in TEMP/W analyses.
F ¼ l
@T
@x
ð1Þ
The governing differential equation used in the formulation
of TEMP/W is shown in Equation (2).

@
@T
@
@T
@T
þ
þQ¼h
ð2Þ
lx
ly
@x
@x
@y
@y
@t
where lx is thermal conductivity in the x-direction, ly is
thermal conductivity in the y-direction, Q is applied heat flux
and h is capacity for heat storage of the soil–water–ice mixture
[32]. This equation states that the difference between the heat
flux entering and leaving an elemental volume of soil at a point
in time is equal to the change in the stored heat energy.
The capacity to store heat is composed of two parts. The
first part is the volumetric heat capacity of the material (either
frozen or unfrozen) and the second part is the latent heat associated with the phase change. Equation (3) describes the capacity of a material to store heat, where, c is apparent
volumetric heat capacity of soil, L is latent heat of water and
Qu is the total unfrozen volumetric water content. Several
equations for estimating unfrozen and frozen volumetric heat
capacity of soil are defined by DeVries [33] and Johnston et al.
[34]. The latent heat associated with phase change can be
ignored in this case because the model presented assumes that
the ground and water contained therein will remain unfrozen
for the period of the analysis, and therefore the change in total
unfrozen volumetric water content (Qu) is equal to zero, so
that the capacity for heat storage of the soil under investigation
Effect of groundwater flow on heat exchangers
is equal to the volumetric heat capacity of the soil. In this case,
Equation (2) can be rewritten as Equation (4).
@Qu
@T

@
@T
@
@T
@T
lx
ly
þ
þQ¼c
@x
@x
@y
@y
@t
h¼cþL
ð3Þ
ð4Þ
In order to include convective heat transfer effects, TEMP/W
must obtain the water and air content and water and air velocity at every gauss point within the model for every time step.
With this information, the partial differential equation for heat
flow [Equation (2)] is modified to Equation (5) (GeoStudio
[29] and Arenson et al. [35]).

_ a TÞ
@Qu @T
@
@T
@ðm
¼
Kt
þ cpa
rs cps þ LQw
@T @t
@y
@y
@y
þ Qw rw cpw
@ðqw TÞ
þQ
@y
ð5Þ
where rscps is the volumetric heat capacity of soil, cpa/w is the
mass specific heat of air or water, Qw is the volumetric water
_ a is the mass flow rate of air, @Qu =@T is the slope of
content, m
the unfrozen water content function, qw is the specific discharge (Darcy velocity) of water and L is the latent heat of
water. Although the definition of Kt is not addressed in
GeoStudio [29] or Arenson et al. [35], DeVries [33] and Shoop
and Bigl [36] defined it using Equation (6), where Kt is
thermal conductivity of the soil – water– ice mixture, Kw is
thermal conductivity of water, Ki is thermal conductivity of
ice, KS is thermal conductivity of soil, Qu is volumetric ice
content and Q0 is soil porosity.
Kt ¼ Kw Qu þ Ki Qi þ Ks ð1 Q0 Þ
ð6Þ
Equation (5) can thus be modified to Equation (7) (where cw
equals the mass specific heat capacity of water (4.187 kJ/kgK)
because this study that the ground and water contained therein
will remain unfrozen for the period of the analysis and that
the ground is fully saturated (no air in the ground).

@T
@
@T
@ðqw TÞ
¼
Kt
þ cw
Qw þ Q
ð7Þ
c
@t
@y
@y
@y
through unsaturated soil (see Richards [37], Childs and
Collis-George [38] and GeoStudio [28]). The only difference is
that under conditions of unsaturated flow, the hydraulic conductivity is no longer a constant, but varies with changes in
water content and indirectly varies with changes in pore water
pressure (see Krahn [39] and Tolooiyan et al. [40]).
The general governing differential equation for 2D see…
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