P17487: Kontiki Kiln Heat Recovery System
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Detailed Design

Table of Contents

Team Vision for Detailed Design Phase

What did your team plan to do during this phase?
  1. Continued development of ANSYS simulation
  2. More in depth testing and analysis of last year's design
  3. Develop proof of concept of convection loop

What did your team actually accomplish during this phase?

  1. Successfully created a convection loop by adapting last year's design
  2. Ordered parts for building our own system
  3. Further developed ANSYS model

Progress Report

An updated progress report can be found here. It summarizes the content on this page and identifies how each team member contributed during this phase.

Prototyping, Engineering Analysis, Simulation

Analysis: Temperature Data

Our team completed a third burn trial to collect temperature data with thermocouples for the reservoir water temperature and hot water inlet time. The details of the testing conditions are outlined in the timeline below:

Timeline of events

Timeline of events


The schematic and actual setup images below show the placement of the thermocouples and the chosen platform height used to complete this test:

public/Detailed Design Documents/Schematics/system_schematic3.png public/Detailed Design Documents/Schematics/kiln_3rd_burn_schematic.png

The final results from the test are summarized below:

Parameter Values
Starting water temperature 14.9 °C 58.82 °F
Increase +17.8 °C +32.04 °F
Ending water temperature 32.7 °C 90.86 °F
Amount of water heated 20 gallons
Time elapsed 1.05 hours
Date completed 11/13/16
Location Victor, NY
Ambient temperature 12.22 °C 54 °F

This test helped prove the concept of the convection loop and that the amount of heat recovered was capable of providing a significant temperature increase in the reservoir water temperature. The heat transfer data from this trial was also used to update our simulation, which is discussed in the next section.

Updated Simulation

For the detailed design phase, the model was further refined from what was first created in the preliminary detailed design phase, and was then used to explore some different design decisions. In the initial simulation, the boundary heat conditions that were initially used did not accurately reflect reality. The amount of heat being lost through the reservoir was not a static amount, but instead depended on the convection being experienced on the walls of the reservoir. To this end, several different simulations were performed with different convection coefficients, in an attempt to match what the model was outputting with what was observed in our testing. Ultimately, a convection coefficient of around 180 was found to properly simulate the test data. The three figures below show the results obtained from this simulation
The velocity vectors obtained from the simulation

The velocity vectors obtained from the simulation


The temperature contours showing the temperature on the outside of the system

The temperature contours showing the temperature on the outside of the system


A volume rendering showing the temperature on the interior of the system

A volume rendering showing the temperature on the interior of the system

After these boundary conditions were found, two other parameters were looked at to see how they affected the model. The first parameter looked at was the diameter of the coils. Increasing the diameter of the coils obviously increases the amount of heat that can come into the system, but we were initially unsure as to whether that would be enough to account for the increased volume of water within the coils. Several different coil diameters, both above and below last years coils in size, were tested, and it was found that increasing the coil diameter significantly increased the average temperature of the water in the reservoir after the hour long burn. This implies that, if water pasteurization was a goal that we wanted to shoot for, that increasing the diameter of the coils would be a good place to start. The height of the reservoir about the top of the coils was also looked at as a parameter to vary, but it was found that it had no affect on the reservoir temperature, only slightly affected the speed at which the water flows through the coils, and can therefore be safely ignored. See below for a graph of the results from the analysis of the coil diameter:

A graph of coil inner diameter vs. average reservoir temperature for 60 minutes

A graph of coil inner diameter vs. average reservoir temperature for 60 minutes

Drawings

The current drawings for our design are tabulated below:
Main Assembly Reservoir Sub-Assembly Kiln Assembly Coil Assembly Platform Assembly
WS-000 (Full System Assembly) RE-100 (Reservoir Assembly) KL-000 (Garden KonTiki Kiln) HE-001 (Coils) PL-100 (Platform)
RE-001 (Tote) HE-002 (Coil Supports)
RE-002 (Lid)
CO-101/-201/-301 (Rigid Aluminum Conduit Fitting)
CO-202/-302 (Wall Galv. Steel Pipe Nipple)
CO-203/-303 (Ball Valve)
CO-204 (Adapter F/M)
CO-102/-304 (Adapter M/M)
CO-103 (Spigot)
CO-205/-305 (Swivel Connector)
CO-206 (Adapter M/F)
CO-306 (Adapter F/F)
CO-207/-307 (Copper Pressure Cup)
CO-208/-308 (Copper Pipe)
CO-209/-309 (Reducer)
Iso-view of coil system from last year

Iso-view of coil system from last year

Below is a drawing to assist the customer and viewers in visualizing the new system:

Representation of final design

Representation of final design

Bill of Material (BOM)

Updated Bill of Materials with total cost of $121.17

Updated Bill of Materials with total cost of $121.17

You can find the up to date BOM here.

Test Plans

After completing 2 testing trials and simulations, the customer and engineering requirements were reanalyzed to assess progress and how well the system meets the demands.

For the customer requirements, the main items for improvement are obtaining local materials for building and safety of operating the system:

Customer requirements

Customer requirements


To address the local materials need, our team will recommend platform height and reservoir sizes which can be created with a user's existing materials (e.g. clay pots for reservoirs). For safety operations, our team will conduct a test specifically for setup and tear down of the system and document the hazards and how to avoid them.

For the engineering requirements, several requirements were dropped from our testing needs and others were limited by location or testing equipment:

Engineering requirements

Engineering requirements

The flame and kiln temperatures could not be measured directly due to the limitation of the thermocouples. However, these requirements turned out not to be as important as actual heat transfer from the kiln to the system, so these requirements will be dropped.

The limitation of the surrounding environment temperature is also of lesser importance since the system will be in direct contact with the kiln. Our team will report on any discrepancies in heat transfer and changes in surrounding temperature.

Training documents and safety assessment will be finalized during MSD II. At this time, our team has identified potential safety risks and how to mitigate them.

The live document can be found here.

Design and Flowcharts

Below is an updated flowchart of the system architecture. Teal boxes indicate a material source. A key safety step has been added to the end of the burn, in which the user must safely remove the coils from the fire to prevent steam discharges. The process to achieve this will become part of the final design.
Systems Architecture for Phase III

Systems Architecture for Phase III

Risk Assessment

Our risk assessment from the Preliminary Design Review carried over to this phase. The risks are grouped by main categories and prioritized by Likelihood:


Risk Assessment

Risk Assessment

The live document can be found here.

Design Review Materials

Include links to:

Plans for next phase

For MSD II, our team requires the kiln and its components to be available on campus for testing purposes. A proposed burn schedule for next semester is shown below:

Spring 2017 burn schedule

Spring 2017 burn schedule

As a team, what do you need to accomplish between now and the end of the semester?

As a team, what do you need to do to prepare for MSD II?


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