Thermal Fluid Project

Department of Mechanical Engineering

ME 440 Project Description Dr. Paul E. Slaboch

Spring Semester 2020

I. Introduction A local company has a new product that they would like to bring to market. The company has designed

and is in the process of testing a micro combined heat and power (mCHP) steam plant. This plant is

intended to heat and provide hot water for small commercial spaces or residential customers. The

mCHP plant is meant to create on-demand heat and hot water, rather than a single distributed system

such as a central furnace and hot water heater tank.

The company has achieved efficiencies in the range of 93-96% in initial testing. However, they are trying

to increase the efficiency of the total system and reduce the amount of losses to the greatest extent

possible. In light of this, they have asked us to redesign the heat exchanger that captures most of the

heat of the steam coming out of the turbine before it is condensed back to water. They also would like

us to take a look at switching out the pump that drives the liquid water/steam circuit of the system. A

full schematic of the system is shown in Figure 1.

Figure 1. Schematic of full mCHP system.

The idea of the heat exchanger is to capture the heat from the steam as it cools and condenses to heat

water for use elsewhere in the building. It is not intended that you will capture the latent heat of

vaporization from the change of state of the steam back into water. The steam should still be steam

when it leaves the heat exchanger. Your task is to design a heat exchanger that will increase the starting

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temperature of the water as high as possible before it enters the boiler exhaust to decrease the amount

of fuel required to create hot water for the building.

Separately, you will need to design and piping system and pump that will drive the water/steam around

the system. The pump draws water from the condenser and pushes it through the vaporization nozzle

where very fine droplets of liquid water are turned into steam almost instantly inside the boiler. The

boiler is a separate heat exchanger that burns natural gas to produce a large amount of heat to create

steam and high enough pressure and temperature to drive the turbine. Your task is to design a piping

system and pump to move the liquid water from the bottom of the condenser up to the boiler as

efficiently as possible.

II. Project specifications This is an open ended design problem in which you must create a heat exchanger that will raise the

temperature as high as possible before the steam enters the condenser (but not to exceed 135 °F). The

steam exits the turbine at a rate of 150 grams/s, a temperature of 300°F, and pressure just below

atmospheric at 13.5 psia. The exhaust from the turbine flows into a 90° bend that flows directly into the

heat exchanger before the steam finally settles in the condensation tank as shown in Fig. 2. The OD of

the exhaust of the turbine is 3.5” and the condenser inlet has an OD of 3”. Once water leaves the

condensation tank, it is pumped up into the boiler and the systems operates as a normal steam plant

from there. The cooling water to be used as hot water throughout the building will enter the system

between 50-60 °F, depending on the season. You are free to set the flow rate of the cold water, but it

must be a minimum of 3.0 gpm. The total mass flow rate of the system must remain constant but these

two fluids have very different densities. The pressure just before the pump is below atmospheric at 13.5

psia with the pressure just past the pump being approximately 35 psia.

Figure 2. Picture showing elbow of steam exiting turbine and entering heat exchanger.

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Your design must include not only a thermodynamic and fluid mechanic analysis of the heat exchanger

and pump system, but also specifications for piping systems and the pump required. You cannot mix the

flow streams, but you do have some latitude regarding the redesign of the steam path coming out of the

turbine. The volume of space in which you must work is fixed at 6 ft3 (3x2x1 rectangular box) for the

heat exchanger with 3 ft in the vertical direction), but you may rearrange the pipe system within that

volume as necessary. The distance from the condenser to the boiler is 4ft vertically, 2 ft laterally, and 2

ft longitudinally. You can place your pump wherever you’d like, as long as the water can get from the

condenser to the boiler. You must take cost and manufacturing into account. The system cost must stay

as low as possible.

III. Report and Evaluation Specifications You only have to do one portion of this project: either the heat exchanger or the pump selection and

piping design. You do not have to do both sides of this. You can choose to work alone or you can work

with a partner. I will be available to help throughout the rest of the semester.

A. Project Deliverables The project deliverables include a final design and pump specification for your system. You must deliver

a detailed report that includes an executive summary and full analysis and justification for design

choices. You will also give a presentation at the end of the semester to discuss your design with your

classmates and instructor.

B. Final Report The final report will be a professional document that includes an executive summary, introduction and

background, design specifications, analysis with design justifications, and final product with all

appropriate engineering drawings and schematics. You must also determine the pump specifications

and find an appropriate pump to power this design. The report should be well written, clear and concise.

References should be used when needed and all figures and tables labeled appropriately. All equations

should be numbered and all symbols should be clearly defined. You are free to break up your report into

however many sections you deem appropriate so that it is easy to follow.

C. Final Presentation The final presentations will be on the last day of class in lieu of a final exam. These presentations are to

be approximately 10 mins each.

If you work as a pair, each student must clearly state what they have worked on as part of this project.

You will be given a single grade for the pair of you. Weekly summaries of activities will be submitted via

Blackboard that lets the instructor know what you accomplished.