MAE 4263

H 6

(25 points)

Problem 1 (5 points)

A house in Medford, Oregon with NLC = 11,800 Btu/F-day and SSF = 9%. Please determine the

auxiliary energy (Btu) required for the house in January. The weather data for Medford, Oregon

for January are: (N=31 days, Daily vertical insolation = 565 Btu/ft2, Heating degree-days = 880

F-days).

Problem 2 (5 points) *

Choose a building on OSU campus that includes passive solar features. Include a photo of the

building and discuss these features and their impact on the energy savings for the building.

Problem 3 (5 points) *

Suggest changes you could make at your house to incorporate passive solar design elements.

* This assignment is related to MAE program outcome (h): an ability to understand the impact of engineering

solutions in a societal context.

Problem 4 (5 points) †

A 100 MW vapor dominated steam power plant uses saturated steam from a geothermal well

with a shut-off pressure of (400 psia). Steam enters the turbine at (80 psia) and condenses at (2

psia). The turbine isentropic efficiency is 0.82, and the turbine-generator combined mechanical

and electrical efficiency is 0.90. The cooling-tower cooling water exit temperature is (70 oF).

Reinjection occurs prior to the cooling tower. Ignore pump work. Please calculate the necessary

steam flow (lbm/h), the cooling water flow (lbm/h), the plant efficiency, and plant heat rate

Btu/kWh.

† This assignment is related to MAE program outcome (a): An ability to apply knowledge of mathematics, science,

and engineering appropriate to the mechanical and aerospace engineering disciplines.

Problem 5 (5 points) ‡

A geothermal power plant utilizes 10 kg/s pressurized hot ground water at 147oC as the heat

source for an organic Rankine cycle. An evaporator consisting of a vertical shell-and-tube heat

exchanger with one shell pass and one tube pass (can be assumed as counterflow heat exchanger)

transfer heat between the groundwater and the counterflowing organic fluid. The organic fluid

enters the shell side as a subcooled liquid at 27 oC and exits the evaporator as a saturated vapor

(quality = 1.0) and temperature = Tsat = 122 oC. Within the evaporator, heat transfer occurs

between liquid ground water and the organic fluid in Stage A with UA = 900 W/m2.K, and

between liquid ground water and boiling organic fluid in Stage B with UB = 1200 W/m2.K. The

organic fluid flow rate is 5.2 kg/s. The specific heat of liquid organic fluid is 1300 J/kg.K and its

latent heat of vaporization is 110 kJ/kg. Please determine the required evaporator heat transfer

surface area for each section (A and B).

‡ This assignment is related to MAE program outcome (c): An ability to design a system, component or process to

meet desired needs.