Since the Project Planning phase, there has been some considerable changes to our system design. Upon further communication with customers and international contacts, the following changes will be made:
- Additional primary function
- Turn untreated water into potable water
- Dry crops
- Added versatility to design criteria
- Height/Dimension adjustablity for Kiln and Soil Pit systems
Team Vision for System-Level Design PhaseFor a complete list of action items our team planned to accomplish during Phase II, please click here.
For a list of actual action items and their progress during this phase, please click here.
Serbian Air-Dryer HRS:
- Takes rising heat from flames to large dryer
- Kiln must run continuously
- Produces marketable charcoal briquettes
Nepal Conduction Water Heater
- Raised system allows for easy biomass feeding
- Must be offset from center for easier loading
- Harnesses rising heat energy
- Distills flowing water through the overhead tubing system
- Requires a large water source (e.g. a hose or water pump)
Nepal Oil Distillation System
- Requires little to no operator intervention
- Uses the rising heat from kiln to heat the specific herbs
- Can produce a marketable amount of oil
- Does not hang exactly over the center of the kiln
Morphological Chart and Concept Selection
Based on the critical functions acquired from the functional decomposition, the Morphological Chart shown below was created. For a chart with words instead of pictures please see the Excel Version.
Each team member then generated at least three concepts from the morphological chart. We then reconvened and as a team narrowed down our concepts to the eight shown below.
Concept SelectionOur team then identified 11 system-level selection criteria that would be useful in comparing the eight concepts.
- Safe for operator
- Easy to operate
- Easy to clean
- Complete in 2 semesters
- Kiln modification
- Quantity produced (of dried leaves and/or clean water)
- Ease to manufacture
- Locally sourced materials
A Pugh chart was then created to compare these concepts with each other using this criteria. In the end, eight Pugh charts were created with the datum being rotated to the next concept each time. The first Pugh chart with concept 1 as the datum is shown below. For all eight charts, please see the complete version here.
Looking solely at the Pugh charts, concept 3 was a clear winner. However, through team discussion, we quickly omitted that option as it could hinder airflow and create unsafe conditions as the kiln is continuously reloaded. Concept 4 was another that we agreed to omit, as it would require an external electrical source like a solar panel to implement.
We were still having difficulty narrowing down our concepts, so we decided to take a new approach by breaking down the concepts into sub-systems and creating different combinations of these sub-systems. This is explained in greater detail in the Concept Development section below.
The HRS can be broken down into two main subsystems. There is an initial heat exchange from the kiln that is then transferred to a second heat exchange that is applied to the unprocessed goods. Concepts were generated for each subsystem separately as shown below.
Found above are concepts for both heat exchange interactions. Each design from the concept generation phase is categorized and analyzed by subsystem.
Each concept is then compared to other concepts in their respective subsystem categories, as well as analyzed in terms of feasibility and how well they fared to the selection criteria. As shown above, several concepts were either refined or scrapped.
Systems Architecture: Designs and Flowcharts
From the system architecture development, four initial and two secondary heat exchange concepts are left for consideration. The following links show combinations of subsystems and their respective functional architecture. Each subsystem was paired based on compatibility of each design (e.i. the working fluid between each exchange has to to be the same.)
- The above pictures display formulas we anticipate using for our heat exchanger 2. Formulas are derived from heat transfer 1 notebook.
- Parameters will need to be defined by the team initially focusing on temperature differences and flow rates.
- NTU is a method of solving these equations based on component dimensions with the use of tables.
- The T-S and the p-H diagrams above will be used in conjunction with steam tables to establish state-point properties.
- These properties will then be used in the boiler equation shown below with the flow rate to establish heat draw.
- Our Phase 1 risk assessment (can be viewed here) focused on potential issues that could occur from a technical, environmental, resource, and safety standpoint to the heat recovery system as a whole. It also highlighted potential issues for our team specifically regarding resources (materials, test locations, and global contacts/technical experts) as we progress through MSD I & II.
- The Phase 2 risk assessment (seen above) focused on specific risks involved with each of our concepts designs for the two methods of heat transfer in our system. These risks covered potential safety and performance issues that we might expect to see within each design concept.
Plans for next phase
Outlined in the link below is the vision and plan for the next phase. It includes deliverables and goals we would like to accomplish by the next review. The ultimate goal is to assign more detail to the proposed design that can then be used to ensure feasibility of our concept(s) through quantification and specificity.