1、Lessons Learned Entry: 0336Lesson Info:a71 Lesson Number: 0336a71 Lesson Date: 1994-07-13a71 Submitting Organization: LARCa71 Submitted by: Bernard LewisSubject: Ram Air Heat Exchanger Provides Increased Cooling Capacity Description of Driving Event: A uniquely designed external ram air exchanger ha
2、s been analyzed and performance tested at the NASA Langley Research Center. The heat exchanger is attached externally to an aircraft and is used to cool a laser system within the fuselage. In the limited space available, with a conventional staggered tube array, estimates showed insufficient cooling
3、 capacity. Thus, a non-conventional design was developed with larger tube and fin area exposed to the ram air to increase the heat transfer performance. The basic design consists of 28 circular finned aluminum tubes arranged in two parallel banks. Wind tunnel tests were performed to simulate air and
4、 liquid flight conditions for both the non-conventional parallel bank arrangement as well as the conventional staggered tube arrangement. Test results are used in a computer model of the heat exchanger to predict the operating performance for the entire flight profile. These analyses predict signifi
5、cantly improved performance over the conventional design and show adequate thermal control margins.Aircraft-borne experiments requiring large electrical power loads create a significant challenge to provide efficient thermal control for a variety of flight environments. Heat dissipation by convectio
6、n within the aircraft is often limited, so the thermal load must be dumped overboard using an external heat exchanger. Due to aerodynamic restrictions, the allowable heat exchanger area outside the aircraft is usually extremely small. Thus, a heat exchanger with a small frontal area must be designed
7、 to meet the stringent thermal requirements of the experiment.For a thorough discussion of this heat exchanger see paper #902019, SAE technical paper series, “Thermal Control of a LIDAR Laser System Using a Non-Conventional Ram Air Heat Exchanger“, by Brian D. Killough, William Alexander, Jr., and D
8、oyle P. Swofford, all of the NASA Langley Research Center, Hampton, Virginia 23665Lesson(s) Learned: Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-A uniquely designed ram air heat exchanger using 28 circular finned tubes, attached externally to an
9、aircraft, provided increased cooling capacity over the conventional staggered tube array.Recommendation(s): Wind tunnel tests performed on the heat exchanger predict significantly improved performance over the conventional design and show adequate thermal control margins.Evidence of Recurrence Contr
10、ol Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): a71 Exploration Systemsa71 Aeronautics ResearchAdditional Key Phrase(s): a71 Aircrafta71 HardwareAdditional Info: Approval Info: a71 Approval Date: 1994-08-11a71 Approval Name: Charles Cockrella71 Approval Organization: AFa71 Approval Phone Number: 804-864-3361Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
