Earth-Coupled Air Conditioner / Heat Pump

Transcription

1 MEMS 1065 Final Report for Design Project 2 Earth-Coupled Air Conditioner / Heat Pump Date: April 20, 2018 Instructor: Dr. Whitefoot Submitted by: Riley Burton Dylan Karas Jack Keegan Bryan Konieczka 1

2 Project Summary: The purpose of this project was to design and evaluate the suitability of a geothermal heat pump that will replace a residential HVAC system. This work is intended to analyze the potential advantages and deficiencies of geothermal heat pumps, comparatively to conventional heating and air conditioning units. The focus of this project was a particular case study where geothermal heating and cooling is under consideration for replacement of a home's existing air conditioner and forced-air natural gas furnace. Thus, an underground heat transfer system was designed and optimized alongside a double pipe heat exchanger and the existing refrigeration system to facilitate the required heating and cooling capacities of the home. Subsequently, the suitability of the design was weighed against the performance, cost-effectiveness, and environmental impact of conventional HVAC systems. The existing refrigeration system was analyzed using F-Chart Software's Engineering Equation Solver (EES) to define the relevant thermodynamic states of the heating and cooling cycles. A double pipe heat exchanger was modeled in Microsoft Excel using the Number of Transfer Units (NTU) method. The two-stage model was developed to simulate heat transfer between the heat transfer fluid and the refrigerant undergoing condensation and evaporation over a portion of the length of the heat exchanger. The heat exchanger was segmented in order to model the differences in exchanger effectiveness for single and two-phase flow. The vertical earth-loop was modeled in Excel through segmentation of the flow lines, simulating the fluid dynamics and thermodynamics of the heat transfer fluid. The interdependent subsystems of the heat pump were optimized simultaneously to preserve the functionality of each component while targeting the design metrics previously mentioned. The final design of the heat pump comprises the existing refrigeration system and a vertical, closed-loop piping system buried underground. A double pipe heat exchanger was designed to interface the two subsystems. Each component of the heat pump was effectively implemented to deliver the required heating and cooling capacities under the constraints set forth by the home and accepted geothermal practices. The design realizes a substantial improvement in system efficiency, equating to an approximated 533% and 10% increase in the performance coefficient associated with the heating and cooling cycles, respectively. Additionally, the heat pump design achieves 5-ton reduction in carbon dioxide (CO2) emissions over the conventional, high-efficiency HVAC system. Because the heat pump operates solely on electrical power, all emissions from the burning of fossil fuels were moved offsite where energy can be generated more efficiently with less environmental impact. The design, however, does not provide costsavings over the lifetime of the system so geothermal replacement of the HVAC system under consideration offers no financial advantage. This shortcoming can be attributed to the sizeable direct and indirect-costs of the heat pump with only a gradual payback through energy savings. Continued work for this project should consider further optimization of the subsystems of the heat pump using cost-reducing measures, beginning with the exploration of alternative earthloop configurations, as this subsystem has the greatest contribution to the net present cost of the overall system. It may also be valuable to weigh the heat pump design against lower-efficiency HVAC systems or conventional systems to be purchased, as the geothermal alternative may be more suitable in these scenarios. 2

3 Table of Contents: Problem Description Analysis Methods Overview of Analysis Refrigeration System Analysis Heat Exchanger Analysis Earth-Loop Analysis Results Design Overview Performance Analysis Cost Analysis Environmental Analysis Conclusion Appendices Bill of Materials Installation Cost Estimate Energy and Maintenance Cost Estimate References and Sources Consulted Meeting Logbook

4 Problem Description: The purpose of this project was to design and evaluate the suitability of a geothermal heat pump that would act as the heating/cooling unit for a moderately-sized home in the Midwest. The pump design would replace the home's existing air conditioner and forced-air natural gas furnace. Additionally, a double pipe heat exchanger replaces the refrigerant-to-air cross-flow heat exchanger in the present air conditioning system. The geothermal heat pump would be comprised of the home's existing refrigeration system (operating in the forward and reverse directions for cooling and heating), an earth-coupled heat transfer line, and a simple concentric tube heat exchanger, interfacing the two subsystems. The design would provide the required heating and cooling capacities for the home and would surpass the performance of the existing HVAC system. The heat pump would also offer cost-savings over the existing system to justify its replacement. Specific components of the project include the design and optimization of the earth-loop, explicitly the layout of the underground piping and pump along with all relevant flow/thermal characteristics of the subsystem. A heat exchanger design would couple the earth-loop to the refrigeration subsystem and provide competitive heating and cooling performance to the existing system. The principal design parameters of the heat exchanger include the sizing of the tubes and the applicable flow/thermal characteristics of the subsystem. These subsystems would be integrated into the existing refrigeration system, which would need modification for optimal performance. The metrics used to measure the quality of the design are its conformity to the requirements and constraints set forth by the home and accepted geothermal practices, in addition to the energy usage, cost-savings of the quoted system, and its environmental impact. The design of the geothermal system is described by the following specifications and constraints: Home Specifications and Heating/Cooling Requirements: Home's square footage: 3000 square feet Constant ground temperature: 11.1 C (below 15 m depth) Required heating capacity: 35.2 kw (120,00 BTU/h) Required cooling capacity: 17.6 kw (5-ton equivalent cooling) Constraints: Heat exchanger and earth-loop must be integrated into the existing refrigeration system (which would be subject to modification) Heat exchanger and pumping system must be sized for placement in the basement of the home Property size available for earth-loop: 30 by 25 m (spaced at least 7.5 m from the home) Heat pump must adhere to accepted geothermal practices 4

5 Analysis Methods: Overview of Analysis The design of this heat pump involves the modeling and optimization of all three subsystems simultaneously, provided that the systems are interdependent and change with each adjustment to the other subsystems. Further intensifying the analysis, the heat pump was designed such that both heating and cooling capacities were met (refrigeration cycle is reversed to provide heating). Thus, the following analysis begins with the heating/cooling capacities of the system, working its way down into the designs of the heat exchanger and earth-loop that would facilitate the required heat transfers. The design flow of the heat pump is displayed in Figure 1. The flowchart displays the linkage between subsystems and the controlling variables passed from one subsystem to its dependent subsystem. Figure 1: Flowchart of the heat pump design Refrigeration System Analysis Heat transfer to and from the home occurs within the first subsystem, the refrigeration cycle. To ensure that the proposed geothermal system matches the requirements of the home, heating and cooling capacities were formulated as driving guidelines for the design. These thermal loads are primarily influenced by the geographic location and size of the home. Figures for the heating and cooling loads per unit area were obtained for the dry, warm climate, and were subsequently paired with the square footage of the home, yielding the heating and cooling capacities for the home, 35.2 kw and 17.6 kw, respectively [1]. DuPont's Suva 410A, the leading hydrofluorocarbon (HFC) refrigerant for residential heat pumps, was used in refrigeration subsystem due to its widespread usage, pressure capabilities, and effective heating/cooling capacities [2]. The refrigeration cycle is a heat pump that represents a very simple closed loop thermodynamic cycle, including four distinct fluid states and four components. The purpose of 5

6 the heat pump is to remove heat from a low temperature source and transfer it to a higher temperature heat sink. The components connecting each of the fluid states are shown in Figure 2. The compressor performs work on the fluid, raising the temperature to facilitate heat transfer against a temperature gradient. At the inlet of the compressor, the fluid was treated as a saturated vapor. The compressor pressurizes the fluid, increasing the temperature until the superheated vapor state is reached. The superheat vapor then flows to the condenser where heat is expelled to the high temperature heat sink. The fluid is a saturated vapor at the exit of the condenser. Fluid pressure is then reduced using isenthalpic capillary tubes, commonly referred to as a throttle, which lowers the temperature of the refrigeration fluid. The fluid then passes through an evaporator where it absorbs heat from the low temperature source and reaches the saturated vapor state before reentering the compressor. Figure 2: Schematic of heating and cooling refrigeration cycles The cycle to the right shows how cooling is performed using the refrigeration system. The evaporator removes heat from the inside air of the home, delivering cool air at approximately 55 F. The condenser then releases the accumulated heat into a heat transfer fluid within the heat exchanger. When the cycle operates in the reverse direction, or when flow is reversed, the refrigeration system acts as a heater (shown in the cycle to the left). In this cycle, the evaporator and condenser are reversed, and heat is transferred from the refrigerant to the home, delivering air at approximately 80 F. The heat exchanger acts as the evaporator and adds heat to the refrigerant. The state conditions of the refrigeration cycle play a major role in the capacity of the heat pump. The typical temperature of the high-pressure side of the cycle is roughly 115 F (46.2 C). This allows heat to be expelled from the system whenever condenser (outdoor air) temperatures are below 115 F. Conversely, the low temperature of typical air conditioning refrigeration cycles is generally near 45 F (7.2 C). This allows heat to be absorbed whenever the evaporator (interior air) temperature is above 45 F. It should also be noted that the temperatures of the 6

7 cooled air expelled in a typical air conditioner are between 55 and 60 F, so the temperature of the refrigeration fluid in the evaporator should be below those temperatures. This provided a baseline for the desired refrigeration state conditions in the analysis of this system. Using F- Chart Software's Engineering Equation Solver (EES) and the assumptions listed below, refrigeration states were chosen in an attempt to minimize compressor work while maximizing specific cooling capacity and facilitating effective heat transfer in the heat exchanger and evaporator. The resulting state conditions are listed below in Table 1. The T-s diagram for the cycle is shown in Figure 3, superimposed onto the saturation line for R410A. Assumptions of State Conditions in the Refrigeration Cycle: State 1: saturated vapor (x1 = 1) Isentropic compression (s2 = s1) Isobaric evaporation/condensation (P3 = P2) State 3: saturated liquid (x3 = 0) Isenthalpic expansion (h4 = h3) Isothermal condensation/evaporation in the heat exchanger (T4 = T1) Table 1: Thermodynamic properties of refrigeration cycle states [3] State Temperature ( C) Pressure Enthalpy Quality (kpa) (kj/kg) Entropy (kj/kg-c)

8 Figure 3: R410A T-s diagram of refrigeration cycle Using the specific enthalpies of the refrigeration states and the heating and cooling loads for the home, the mass flow rate of the refrigeration system was determined using the relation shown in Equation 1. The specific enthalpies of each state, paired with the mass flow rate of the refrigerant, can then be used to determine the heat transfer required in the heat exchanger and the input power of the compressor, given in Equation 2 and Equation 3, respectively. The mass flow rate, state temperatures, and the heat transfers serve as several of known input parameters for the design of the heat exchanger. where, Q heating = m (h 2 h 3 ) Q cooling = m (h 1 h 4 ) (1) Q e,heating = m (h 1 h 4 ) Q e,cooling = m (h 2 h 3 ) (2) W c,heating = m (h 2 h 1 ) W c,cooling = m (h 2 h 1 ) (3) Q represents the heating/cooling loads of the home Ẇ represents the input power of the compressor ṁ represents the mass flowrate through the refrigeration system h represents the specific enthalpy of a given state 8

9 Known Input Parameters: Required heating and cooling capacities Quality at states 1 and 3 Optimization Parameters: Operating temperatures (defined by states 1 and 3) Output Parameters of Interest: All unknown thermodynamic properties for each state Mass flow rate of the refrigerant Input power of the compressor Heat Exchanger Analysis The proposed concentric tube heat exchanger serves as the interface between the refrigeration and earth-loop subsystems, transferring heat between the two through the mechanism of convective heat transfer. Within Microsoft Excel, the heat exchanger was modeled in two stages, both encompassing a length of concentric tubing with the refrigerant flowing through the inner tube and heat transfer fluid flowing through the annulus. Given the two-phase refrigerant flow across a portion of the exchanger length, the governing equations associated with heat transfer differ for each segment. The Number of Transfer Units (NTU) method was employed using the appropriate effectiveness expressions for each section and the sections were arranged serially, completing the model for the entire heat exchanger. The effectiveness for single-phase and two-phase heat transfer for concentric tube heat exchangers is given in Equation 4 and Equation 5, respectively. Equation 6 and Equation 7 give the expressions for the number of transfer units and the capacity ratio for the fluid flows. ε = 1 e[ NTU(1 C r )] 1 C r e [ NTU(1 C r )] ε = 1 e NTU NTU = U oa o,tube (m C p ) min (4) (5) (6) C r = C min C max = (m C p) min (m C p ) max (7) where, Uo = overall heat transfer coefficient Ao,tube = outer surface area of the inner tube (ṁcp)min = lesser capacity of the two fluid flows (ṁcp)max = greater capacity of the two fluid flows 9

10 Now equipped with the heat transfer effectiveness for each type of fluid flow, the outlet temperatures for both fluids were computed and subsequent calculations led to figures for the heat transferred in each stage. Due to the reversibility of the refrigeration cycle, it is important to note that the fluids flow through the heat exchanger in opposite directions (counter flow) when the system operates as a heater, and the same direction (parallel flow) when it operates as an air conditioner. Although parallel flow is often associated with inferior heat transfer effectiveness, it is actually equivalent to the effectiveness related with counter flow for the cooling cycle, due to the isothermal evaporation of the refrigerant along the entire length of the heat exchanger. Consequently, the temperature difference profiles for both flow directions are equivalent. The complete analysis can be found in Design of Fluid Thermal Systems, by William S. Janna. The heat exchanger model was then optimized to yield the required heat transfers for both heating and cooling cycles. Given the mass flow rate of the refrigerant and the inlet and exit temperatures (predetermined in the refrigeration cycle analysis), the size and tube geometry of the heat exchanger (in addition to the flow rate and operating temperatures of the heat transfer fluid) were augmented until the desired exit temperatures and aggregate heat transfer were reached. The principal modeling parameters are summarized below. Known Input Parameters: Exchanger inlet and exit temperatures of the refrigerant Mass flow rate of the refrigerant Required heat transfer for the heating and cooling cycles Optimization Parameters: Exchanger length Inner tube and annulus geometries (nominal diameters) Mass flow rate of the heat transfer fluid Operating temperatures of the earth-loop Output Parameters of Interest: Exchanger exit temperature of the heat transfer fluid 10

11 Earth-Loop Analysis Cycling heat transfer fluid through the heat exchanger into deep vertical boreholes, the earth-loop was modeled in Excel as three identical lines of piping, each branching out from the central supply and feed lines extending out from the basement of the home. Given that each of the paths are identical, the mass flow rates, pressure profiles, and thermal characteristics are matched for each path and thus, only one needed to be modeled. Within the vertical paths, piping was further discretized into short segments (one meter in length) accurate fluid dynamics and thermodynamic modeling. The segmented model offers the ability to adjust temperaturedependent properties of the heat transfer fluid along the length of the piping instead of averaging properties over longer lengths (which produces are less robust model). The complete procedure for modeling pipe flow and pressure losses, as well as thermodynamic computations used to quantify heat flow can be found in Design of Fluid Thermal Systems, by William S. Janna. The modeled piping subsystem was controlled using numerous known parameters and only one variable subject to optimization. Listed below, the parameters associated with the layout of the pipe lines, pipe geometry, and the thermal properties of the ground (listed first) were set to align with accepted geothermal practices [4]. The inlet temperature and mass flow rate of the heat transfer fluid are also known, as they were optimized in the heat exchanger analysis. Note that the exit temperature of the piping system (inlet temperature to the heat exchanger) is also known from the preceding analysis. Total heat transfer in the exchanger was computed using the heat capacity and temperature change of the heat transfer fluid. Thus, the same heat transfer is achieved in the earth-loop if the fluid is returned to the temperature assumed at the inlet of the exchanger. This leaves the size (depth of the boreholes) of the subsystem as the only optimization parameter. To verify that the heat transfer requirements are met, the principal flow characteristics and aggregate heat transfer to or out of the subsystem are computed by the model. Known Input Parameters: Spacing from house (supply and return lengths): 7.5 m Borehole spacing: approximately 5 m Supply and return header lengths: 4 m Tubing dimensions: 1" nom. diameter high-density Polyethylene (PEH) tubing Tubing roughness factor and thermal conductivity: 3 µm and 0.5 W/m-k Ground temperature (constant below 15 m depth): 11.1 C Thermal conductivity of grouting mixture: 2.77 W/m-k Inlet temperature and mass flow rate of the heat transfer fluid Optimization Parameters: Borehole/path depth Output Parameters of Interest: All relevant flow and thermodynamic characteristics Exit temperature of the heat transfer fluid (verified with the previously determined temperature) Cumulative heat transfer to or from the piping subsystem Pressure losses and consequential pumping requirements 11

12 Results: Design Overview The geothermal heat pump has been designed to modify the elements of the house s existing refrigeration system to satisfy the necessary cooling and heating requirements of the house while achieving reduced greenhouse gas emissions and lifetime cost-savings. The condenser of the air conditioner was replaced with a concentric tube heat exchanger that receives and expels heat from a geothermal heat transfer piping system. The final system schematic can be seen below in Figure 4. Figure 4: Schematic of heat pump design 12

13 The designed concentric tube heat exchanger acts as the interface between the internal refrigeration system and external geothermal ground loop. The optimization of its design accounted for the effect that the overall length, inner tube diameter, and annulus diameter has on both interdependent subsystems. The results of the optimization yielded an overall length of 10 m with a 1 nom. diameter inner tube and a 1.25 nom. diameter annulus. The mass flow rate of R410A in the inner tube is kg/s for heating and kg/s for cooling while the mass flowrate of DOWFROST GEO 20 through the annulus is kg/s for heating and kg/s for cooling. The heat exchanger is wrapped in 1 thick fiberglass insulation to minimize heat loss. The optimization process of the geothermal ground loop involved reducing the overall size of the subsystem while still achieving the required heating and cooling capacities. The ground loop features three parallel, 85 m vertical boreholes with 1 nom. diameter, high-density polyethylene piping in order to meet the requirements of the system. All boreholes surrounding the piping would be filled with thermal grouting to promote effective heat transfer. The design results in a maximum pressure loss of 34 psi and requires the use of a centrifugal pump with 1/3 horsepower capacity. Performance Analysis The geothermal heat pump matched the required 35.2 kw heating capacity and 17.6 kw cooling capacities of the existing system while eliminating the system s dependence on natural gas. Table 2 provides the relevant performance characteristics for the heat pump and the existing system for both heating and cooling. Although the operation of the heat pump draws more electrical power than the existing system, the overall energy consumed by the system is smaller, as the burning of natural gas is eliminated (which equates to approximately 36.7 kw in the forced-air natural gas furnace). The heat pump also realizes an improvement in cooling efficiency, which can primarily be attributed to the decreased heat rejection temperature. Consequently, the coefficients of performance associated with each cycle show improvement over the conventional HVAC system. Table 2: Relevant performance characteristics for the heat pump design and existing system Performance Characteristic Heating Cooling Heat Pump Existing System Heat Pump Existing System Thermal Capacity (kw) Power Draw (kw) Natural Gas Heat Energy (kw) Coefficient of Performance

14 Cost Analysis When comparing the effective cost of running a conventional HVAC system to a geothermal heating and cooling system, it is important to assume a lifetime of each system to calculate maintenance, energy, and net present costs. Table 3 displays the cost breakdown for both systems over a 20-year lifespan for an average sized home in Nevada. It is worth noting that there are no direct or indirect costs associated with the existing system because we assumed that the geothermal system would be replacing the existing HVAC system. The overall costs associated with the geothermal heat pump are substantially lower than the current HVAC system, but the net present cost (using a conservative discount rate of 8%) is over $8,000 greater. This is due in part by the associated upfront costs in replacing the existing HVAC system of the home as well as a higher overall maintenance cost as the heat exchanger must be cleaned periodically to prevent fouling from diminishing the system s performance. Table 3: Projected system costs and net present cost analysis assuming 20-year lifetime Cost Component Heat Pump Existing System Direct $ 6, Installation (Indirect) $ 7, Maintenance $ 1, $ Energy $ 27, $ 39, Total Cost $ 42, $ 47, Net Present Cost $ 28, $ 20, The bill of materials, installation cost estimate, and energy and maintenance cost estimate can be found in their respective sections of the appendices. One major cost benefit of the geothermal system is a substantially reduced energy bill over the span of 20 years. While the geothermal system may not be the most cost effective when looking at the net present value of the cooling system, the average money spent on fuel to run the system is much lower. This means the overall yearly cost of geothermal system is lower than the conventional HVAC system, and therefore will return more money over any lifetime above 20 years. One way to improve the overall cost effectiveness of the geothermal system is to use it as a replacement for outdated systems instead of high efficiency HVAC systems. Older systems are less efficient and require higher maintenance costs than a high efficiency HVAC system, and would therefore cost a substantially larger amount of money to run and maintain over a 20-year lifetime when compared to a geothermal replacement. It would be more appropriate to implement a geothermal system when constructing new homes. Because the analysis in the above table does not take into consideration the direct and indirect costs of implementing an HVAC system, a geothermal may prove to be a more cost-effective system over a 20-year lifetime for a newly constructed home due to its lower fuel costs and overall cost associated with construction and operation. 14

15 Finally, other types of heat exchangers such as plate and shell and tube heat exchangers can be investigated for efficiency, sizing, and overall costs associated with them to reduce the capital investment required to create a geothermal heat pump. The heat exchanger used for this analysis is a considerably large system to accommodate for the required heating and cooling of the home. It may be possible to replace a double pipe heat exchanger with a more appropriately sized heat exchanger of a different kind, which may lead to higher efficiency, easier maintenance, and overall lower costs of construction and maintenance. Environmental Analysis One of the main benefits of replacing a conventional HVAC system with a geothermal heat pump is the reduction in fuel costs. Not only does this reduce the overall cost associated with the operation of the system, it also reduces the overall carbon footprint produced by burning fossil fuels for electricity and burning natural gas to heat the refrigerant. Table 4 gives the annual carbon dioxide emissions of the heat pump and the existing, conventional HVAC system side by side for comparison. Table 4: Overview of annual CO2 emissions for the heat pump design and existing system Component of Annual CO2 Emissions Heat Pump Existing System Emissions from Power Plant 8.5 tons 4.8 tons Emissions from Natural Gas tons Total Annual Emissions 8.5 tons 13.6 tons At first glance, it would appear that operating the geothermal heat pump produces more carbon emissions when considering the electrical draw required to run the refrigerant cycle as well as the pump required to circulate the heat transfer fluid through the earth-loop. This does not tell the whole story however, as the operation of the HVAC system requires burning natural gas to produce heat within the system. When comparing the overall carbon emissions, it is clear that the geothermal heat pump decreases the carbon dioxide produced by over five tons on an annual basis. Over the span of the lifetime of each system this corresponds to a total decrease of 102 tons of carbon dioxide. 15

16 Conclusion: In summary, the proposed heat pump design effectively integrates the vertical, closedloop piping system with the home s existing refrigeration system. Additionally, the double pipe heat exchanger design effectively interfaces the two subsystems to deliver the heating and cooling requirements of the home. The design realizes a substantial improvement in system efficiency for both heating and cooling cycles and provides a reduction in CO2 emissions over the conventional, high-efficiency HVAC system. The design, however, does not provide costsavings over the lifetime of the system, so geothermal replacement of the HVAC system under consideration offers no financial advantage. This shortcoming can be attributed to the sizeable direct and indirect-costs of the heat pump with only a gradual payback through energy savings. Continued work for this project should consider further optimization of the heat pump s subsystems considering cost-reducing measures. First and foremost, the use of alternative earthloop configurations should be explored to improve cost-savings, as this subsystem has the greatest contribution to the net present cost of the overall system. It may also be valuable to weigh the heat pump design against lower-efficiency HVAC systems or conventional systems to be purchased, as the geothermal alternative may be more suitable in these scenarios. 16

17 Appendices: Bill of Materials Bill of Materials BOM Part Unit of Part Name Quantity Level Number Measure Unit Cost Total Cost 1 1 Existing Refrigeration System 1 Each Existing Capillary Tubing 1 Each Existing Evaporator Piping 1 Each Existing Fan 1 Each Existing Air Condition Unit and Compressor 1 Each DuPont Suva 410A Refrigerant, 25 lb. Canister 1 Each $ $ Double Pipe Heat Exchanger 1 Each " Nominal Diameter, Thin-Wall (Schedule 10), 304/304L Stainless Steel, Unthreaded Pipe, 6 ft. Length 5 Each $ $ /2" Nominal Diameter, Standard Wall (Schedule 40), 304/304L Stainless Steel, Unthreaded, Welded Pipe, 6 ft. Length 5 Each $ $ /2" Nominal Diameter, Standard Wall (Schedule 40), 304/304L Stainless Steel, Unthreaded Tee Connector 10 Each $ $ Owens Corning 1" Fiberglas Pipe Insulation, 3 ft. Length 10 Each $ $ Vertical Earth-Loop 1 Each " Nominal Diameter, Flexible, High-Density Polyethylene Plastic Piping, 500 ft. Length 4 Each $ $ 1, " Nominal Diameter, Low-Pressure, Polypropylene Tee Connector 6 Each $ 1.62 $ " Nominal Diameter, Socket Fusion, Polyethylene U-Bend 3 Each $ 9.95 $ GeoPro Thermal Grout Select Premium Bentonite Grouting, Pallet 1 Each $ $ GeoPro PowerTec (Graphite Thermal Enhancement Compound), Pallet 1 Each $ $ High-Efficiency Centrifugal Circulation, 120/ V AC, 1/3 hp Pump 1 Each $ $ The Dow Chemical Company DOWFROST GEO 20, 55 Gallon Barrel 3 Each $ $ 1, Total Direct-Cost: $ 6,

18 Installation Cost Estimate Installation Cost Estimate Component Description Quantity Unit of Measure Unit Cost Total Cost 1 Excavation 20 Cubic Meter $ $ 1, Borehole Drilling 285 Meter $ $ 5, Labor $ Total Installation Cost (Indirect-Cost): $ 7, Energy and Maintenance Cost Estimate Energy and Maintenance Cost Estimate Component Description Quantity Unit of Unit Measure Cost Total Cost 1 Annual Heating Electricity kwh $ 0.12 $ Annual Cooling Electricity kwh $ 0.12 $ Annual Maintenance $ Total Annual Operating Cost: $ 1, Total Operating Cost Over 20-Year Lifetime: $ 28,

19 References [1] How to Size Your Air Conditioner or Heater, HVAC Direct, [2] DOWFROST GEO 20 Technical Data Sheet, The Dow Chemical Company [3] Pseudo-Pure Fluid Equations of State for the Refrigerant Blends R-410A, R-404A, R-507A, and R-407C, E. Lemmon (obtained in EES) [4] Olgun C., Introductory Overview of Ground Source Heat Pump Technologies, Virginia Tech Sources Consulted MEMS 1065 Design Project 2 Deliverables and Detailed Description Handout, ME Dept., University of Pittsburgh MEMS 1065 Project Idea 5 - Earth Coupled Air Conditioner and Heat Pump Handout, ME Dept., University of Pittsburgh MEMS 1065 Course Lectures, ME Dept., University of Pittsburgh Design of Fluid Thermal Systems, Janna W. Thermodynamic Properties of DuPont Suva 410A Refrigerant, E. I. du Pont de Nemours and Company DOWFROST GEO 20: Propylene Glycol-Based Heat Transfer Fluid for Geothermal Heat Pump Systems, The Dow Chemical Company MEMS 1065 Pipe Friction Tables Handout, ME Dept., University of Pittsburgh MEMS 1065 Economic Analysis Handout, ME Dept., University of Pittsburgh 19

20 Meeting Logbook Logbook Entry 1 Date: March 13, 2018 Time(s): 2:30 PM Group Members Present: Riley Burton, Dylan Karas, Jack Keegan, Bryan Konieczka Logkeeper: Riley Burton Items Discussed: Project overview Tasks Assigned: Research geothermal heat pumps Research refrigeration cycles Research double pipe heat exchangers Tasks Completed: Developed an understanding of the project Logbook Entry 2 Date: March 18, 2018 Time(s): 2:00 PM Group Members Present: Riley Burton, Dylan Karas, Jack Keegan, Bryan Konieczka Logkeeper: Dylan Karas Items Discussed: Project definition Project deliverables Project approach Analysis methods Tasks Assigned: Define required heating and cooling capacities Define refrigeration cycle operating states Recreate piping system model for horizontal earth-loop Tasks Completed: 20

21 Researched geothermal heat pumps Researched refrigeration cycles Researched double pipe heat exchangers Set project definition and deliverables Set intended project approach Logbook Entry 3 Date: March 20, 2018 Time(s): 2:30 PM Group Members Present: Riley Burton, Dylan Karas, Jack Keegan, Bryan Konieczka Logkeeper: Jack Keegan Items Discussed: Horizontal earth-loop modeling Two-phase heat exchanger modeling Subsystem integration Tasks Assigned: Complete earth-loop model Tasks Completed: Completed refrigeration state definitions Logbook Entry 4 Date: March 22, 2018 Time(s): 2:30 PM Group Members Present: Riley Burton, Dylan Karas, Jack Keegan, Bryan Konieczka Logkeeper: Bryan Konieczka Items Discussed: Preliminary report deliverables Tasks Assigned: Begin preliminary report Tasks Completed: 21

22 Completed earth-loop model Logbook Entry 5 Date: March 25, 2018 Time(s): 3:30 PM Group Members Present: Riley Burton, Dylan Karas, Jack Keegan Logkeeper: Riley Burton Items Discussed: Preliminary report problem statement Analysis methods Overview of preliminary design Tasks Assigned: Complete preliminary report analysis methods Project summary Next steps Preliminary component selection Tasks Completed: Preliminary report problem statement Overview of preliminary design Logbook Entry 6 Date: March 28, 2018 Time(s): 1:00 PM Group Members Present: Riley Burton, Dylan Karas, Jack Keegan, Bryan Konieczka Logkeeper: Dylan Karas Items Discussed: Review of preliminary report Tasks Assigned: None 22

23 Tasks Completed: Completed preliminary report Logbook Entry 7 Date: April 3, 2018 Time(s): 2:30 PM Group Members Present: Riley Burton, Dylan Karas, Jack Keegan, Bryan Konieczka Logkeeper: Jack Keegan Items Discussed: Peer review of preliminary report Tasks Assigned: Complete peer review of preliminary report Review preliminary report comments Complete heat exchanger model Optimize refrigeration state definitions Recreate piping system model for vertical earth-loop Tasks Completed: None Logbook Entry 8 Date: April 10, 2018 Time(s): 2:30 PM Group Members Present: Riley Burton, Dylan Karas, Jack Keegan, Bryan Konieczka Logkeeper: Bryan Konieczka Items Discussed: Finalization of heat pump design Tasks Assigned: Finalize heat pump design Finalize component selection Tasks Completed: 23

24 Completed peer review of preliminary report Reviewed preliminary report comments Completed heat exchanger model Optimized refrigeration state definitions Completed piping system model for vertical earth-loop Logbook Entry 9 Date: April 12, 2018 Time(s): 2:30 PM Group Members Present: Riley Burton, Dylan Karas, Jack Keegan, Bryan Konieczka Logkeeper: Riley Burton Items Discussed: Final presentation Performance analysis Cost analysis Environmental analysis Tasks Assigned: Complete final presentation Tasks Completed: Finalized heat pump design Finalized component selection Logbook Entry 10 Date: April 15, 2018 Time(s): 11:00 AM Group Members Present: Riley Burton, Dylan Karas, Jack Keegan, Bryan Konieczka Logkeeper: Dylan Karas Items Discussed: Presentation run-throughs Tasks Assigned: 24

25 Begin final report Project summary Problem description Analysis methods Results Tasks Completed: Completed final presentation Logbook Entry 11 Date: April 16, 2018 Time(s): 8:00 PM Group Members Present: Riley Burton, Dylan Karas, Jack Keegan, Bryan Konieczka Logkeeper: Jack Keegan Items Discussed: Final report analysis methods Results Conclusions Tasks Assigned: Final report analysis methods Results Conclusions Tasks Completed: Final report project summary Problem description Logbook Entry 12 Date: April 19, 2018 Time(s): 8:00 PM Group Members Present: Riley Burton, Dylan Karas, Bryan Konieczka Logkeeper: Bryan Konieczka Items Discussed: 25

26 Final report analysis methods Results Conclusions Tasks Assigned: None Tasks Completed: Completed final report 26