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Improving Cabin Thermal Comfort by Controlling Equivalent Temperature

SAE International Journal of Aerospace

ThermoAnalytics, Inc.-Allen R. Curran, Scott D. Peck, Tony J. Schwenn, Mark A. Hepokoski
  • Journal Article
  • 2009-01-3265
Published 2009-11-10 by SAE International in United States
An aircraft environmental control system (ECS) is commonly designed for a cabin that has been divided into several thermal control zones; each zone has an air flow network that pulls cabin air over an isolated thermocouple. This single point measurement is used by the ECS to control the air temperature and hence the thermal environment for each zone. The thermal environment of a confined space subjected to asymmetric thermal loads can be more fully characterized, and subsequently better controlled, by determining its “equivalent temperature.” This paper describes methodology for measuring and controlling cabin equivalent temperature. The merits of controlling a cabin thermal zone based on its equivalent temperature are demonstrated by comparing thermal comfort, as predicted by a “virtual thermal manikin,” for both air-temperature and equivalent-temperature control strategies.
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Thermal Analysis and Simulations for Optimizing HVAC Load on Heavy Trucks

ThermoAnalytics, Inc.-Amit B. Shah, Craig M. Cless, John S. Curlee
Volvo Trucks NA-Jeremy Edmondson
Published 2008-10-07 by SAE International in United States
This paper summarizes investigation into the strategies, methods, and best practices for achieving low HVAC load on two existing vehicles programs. Decreasing the load required from the HVAC system will help improve the fuel economy of the truck resulting in a cost savings to the customer.A thermal analysis was performed on two truck cabin interiors to calculate the amount of energy necessary to maintain a desirable internal cabin air temperature while under certain environmental conditions. In order to quantify how much cost is associated with running the HVAC system with its current design, the thermal analysis was coupled with a computational fluid dynamics simulation to understand the complicated flow patterns inside the cab while the HVAC system is operational. The load on the HVAC system was calculated for each scenario using the thermal model and the results were compared to the benchmark. These results were then used to help quantify the most cost effective solutions to improve the performance of the HVAC system and hence reduce the energy consumed to maintain cab comfort.
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Modeling Human Thermoregulation as a Means of Evaluating Heat Stress Events

ThermoAnalytics, Inc.-Allen R. Curran, Peter L. Rynes
Published 2008-08-19 by SAE International in United States
This paper presents methodology for predicting body core temperature using the ASHRAE two-node thermoregulation model. Predicted changes in core temperature can be used to certify that, during a heat stress event, the temperature and humidity within an aircraft will not exceed values that are hazardous to the occupants. The use of ASHRAE model was validated by comparing its predictions to experimental data for subjects that were exposed to hot (33° to 48°C) environments. The model has been used to predict body core temperature in the cockpit and cabin during three different environmental ventilation system failure simulations for an aircraft that uses atmospheric air from the ram air duct in the event of a dual pack failure.
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Adapting Segmental Models of Human Thermoregulation and Thermal Sensation for Use in a Thermal Simulation of a Vehicle Passenger Compartment

ThermoAnalytics, Inc.-Allen Curran, Mark Hepokoski, John Curlee
Michigan Technological Univ.-David Nelson, Abhishek Biswas
  • Technical Paper
  • 2006-05-0043
Published 2006-10-22 by Society of Automotive Engineers of Japan in Japan
This paper presents the method by which a multi-segmental human thermoregulation model and a thermal sensation model were adapted to predict human comfort in a thermal simulation of a vehicle passenger compartment.The thermoregulation model was modified to calculate tissue temperatures for a human body described by a surface mesh. A mesh is essential to the calculation and application of nonuniform boundary conditions (solar loading, radiation, conduction and convection) present in a vehicle passenger compartment. Temperatures calculated by the modified thermoregulation model were subsequently used in a mathematical model for predicting thermal sensation. The resulting thermal comfort model was validated by comparing the predicted thermal sensation of a sedentary passenger in a range of mild, steady-state environments to the corresponding Predicted Mean Vote (PMV) associated with each environment.The process for predicting human comfort is discussed including the generation of a mesh of suitable fidelity, the implementation of the thermoregulation model and the determination of localized clothing resistance values from whole-body values.

A virtual prototyping tool for heat and signature management design

ThermoAnalytics, Inc.-K. Johnson, A. Curran, D. Less
U.S. Army TACOM-T. Gonda, J. Jones
  • Technical Paper
  • 1999-25-0128
Published 1999-06-14 by ISATA - Dusseldorf Trade Fair in United Kingdom
In this age of rapid prototyping and advanced signature and heat management designs, a new thermal modeling and simulation tool is being developed. The U.S. Army awarded a Small Business Innovation Research (SBIR) Phase II program at the end of 1997 to create a new design tool called MuSES (Multi-Service Electro- optics Signature) code capable of meeting these arising requirements. Because of the strong connections between signature management for military ground vehicles and heat management for commercial automobiles, there is considerable dual-use collaboration and commercial commitments from the automobile industry. This SBIR program will create an innovative design tool for the military and provide considerable technology transfer to other government and industrial organizations. A key ingredient to the success of this modeling tool is the conversion of solid CAD geometry into a faceted mesh. In addition, US Army TACOM engineers are developing a software package (called Eclectic) to convert solid CAD geometry into a faceted mesh to feed the MuSES 3-D Model Editor. A description of this work is detailed in this paper.