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A computer model of a plant growth chamber, capable of both steady-state and transient simulations, has been developed to assess the performance and design of bioprocessors. Two approaches that employ a spreadsheet program and a simulation package to estimate system mass and energy balances are used. Parameters that describe hardware and plant characteristics are input to the model. The model provides predictions of the environmental conditions in the growth chamber, the production of biomass, the exchange of carbon dioxide and oxygen, and the transpiration of water. The model has been customized to characterize the Salad Machine at NASA Ames Research Center. Predictions resulting from the simulation of the customized model are compared with hardware test data for model validation.

The tests outlined in this paper were used to characterize the hardware components of the Salad Machine, a small NASA-developed bioprocessor. The data from these tests are presented, and the methods by which this data can be integrated into system mathematical models are briefly discussed. The subsystems and physical processes discussed include the lighting system, the air loop (condensing heat exchanger and the blower), heat transfer to the surroundings, and leakage. Through this effort it was learned that in the development of a test protocol, care should be taken to order the tests such that environmental parameters, particularly humidity, require as few large adjustments as possible. Sensor calibration and installation take a substantial amount of time, which should be built into the test schedule. Two properties were particularly hard to quantify: the air flow rate and the energy from the lighting system entering into the growth volume.