SteriSpace - 300 cfm Model
The 300 CFM unit uses a positive displacement blower to move and compressively heat the airflow. The blower has a twisted tri-lobe rotor and has proven performance as the main component. A counterflow heat exchanger minimizes system power requirements by preheating the contaminated air stream by the transfer of energy from the high temperature blower outflow. The heat exchanger reduces the system outflow temperature to levels appropriate for introduction into habitable spaces or an HVAC system.
The motor is powerful enough to maintain the treatment temperature in thermal equilibrium. An electrical resistance heater heats the incoming flow before thermal equilibrium is reached, and after that it can be used intermittently to maintain the treatment temperature. This allows to reduce the time required to reach thermal equilibrium from more than an hour to less than 20 minutes. As an alternative, the device could also be operated with a valve on the inlet to maintain the operating temperature.
The overall control of the unit is through a Programmable Logic Controller (PLC), housed within its own enclosure and functions as a master to operate the SteriSpace system. The control parameters (e.g., target blower outlet temperature) are entered using a PC interface and the system can be started from a single input signal (manual push button, PC start signal, or other external signal). Thereafter, the control module manages the system through start-up and steady-state operating modes. Its PLC circuit is programmed to provide optimized operating conditions by maximizing the volumetric airflow while maintaining the target outlet temperature. It will also recognize abnormal operating conditions that may be detrimental to the system (e.g., excessive temperatures, loss of airflow) and will automatically execute emergency shut-down procedures.
The device attains the designed operating conditions quite well. The flow rate specification is met at an operating pressure ratio of 1.07, essentially at the design value. Independent biological testing with hardy spores demonstrated that the 300 CFM Prototype maintained better than six nines kill effectiveness. At 240°C treatment temperature, the percentage destroyed was >99.9999%. No surviving spores were observed downstream of the device. Similar test results have been obtained with vegetative bacteria and a virus. Further testing demonstrated that viruses can be killed at lower treatment temperatures, and hence lower power consumption.
SteriSpace - 5000 cfm Model
This unit provides a Wide Area Collective Protection system for the protection of buildings against a biological attack or event. It was developed for U.S. Army Corps of Engineers (USACE), Engineering Research Center (ERDC). Our patented technology of compressive heating to destroy airborne biological contaminants was applied.
A mobile 5,000 cubic feet per minute (CFM) SteriSpace model was designed to protect a building or buildings from a biological threat. Our approach to providing biological collective protection to buildings in a developed area or an expeditionary setting uses mobile 5,000 CFM systems. One or more systems are transported on trailers and connected to the make-up air duct in a building with an HVAC system or to an opening, e.g. door or window, in a building without an HVAC system.
The 5,000 CFM prototype system is shown in the drawing without the insulation. The unit has been transported over highways to test sites. It has been operated with shore power and a field generator.
Testing of the 5000 CFM prototype with an Environmental Control Unit (ECU) was completed at the HDT Global facility in Geneva, OH. The prototype was powered with an HDT 60 kW model HMMWV Towable Trailer Generator. The ECU was connected to a 35 kW Generator ECU Trailer (GET), providing an eight-ton cooling capability. The objectives of this test were to demonstrate operational compatibility with military field equipment as well as to demonstrate that the outlet flow from the prototype can be cooled to conditions suitable for use in an inhabitable space. Outlet temperatures below ambient were measured.
The unit was transported to Research Triangle Institute in Durham, NC for independent biological testing. Testing was done with hardy biological (Bg) spores. At a treatment temperature of 240oC, complete kill to the level of detection was observed. No viable spores were detected downstream of the system corresponding to a kill effectiveness > seven logs.
While the prototype described was designed, built and tested for the U.S. Department of Defense, it has widespread application in commercial buildings as well. The unit can be at a fixed site and integrated with a building air handling system. The most efficient process for integration in a building air handling system would be to incorporate the system in the building design at the outset.