Thermal management and temperature control of a containerised rapid deployment radar system

Jeggels, Yusuf Umar (2008-03)

Thesis (MScIng) -- University of Stellenbosch, 2008.

Thesis

ENGLISH ABSTRACT: The thermal problems of the ESR 220 radar system (Kameelperd) have been investigated. To address this and other potential thermal problems a thermal management design process methodology was developed. The transistors in the high power amplifier (HPA), within the radar equipment container (REC), failed due to thermal shock and excessively high temperatures at high system container air temperatures. The only way to ensure that the transistors in the existing design do not overheat is to cool the system container air to a temperature well below the comfort level of the operating personnel. The four processor boards of the digital signal processors (DSP) exceed their temperature specification if the fans inside the DSP are switched off. The thermal management design process methodology was used to analyse the Kameelperd, which resulted in the air flow inside the REC and the existing HPA cooling solution being analysed. Alternative HPA cooling solutions need to be explored as possible replacements for the existing HPA cooling solution. Flomerics FLOTHERM computational fluid dynamics program was used to analyse the air flow through the REC. The analysis showed that the inappropriate positioning and configuration of the various units in the REC not only limits the total air flow rate through the container, but also inhibits the distribution of air to the DSP processors. It is proposed that the receiver front end and driver amplifier be redesigned such that they are open in the horizontal plane. In addition the positioner interface must be removed and the electromagnetic interference (EMI) shield at the entrance of the REC be replaced or removed. The proposed changes will improve the total air flow rate and the distribution of the air flow inside the REC. If the proposed changes are to be applied to the REC, then the system container air flow exit configuration needs to be changed. A numerical model, based on experimental data of the existing HPA cooling solution, was used to calculate the HPA transistor base temperature and determined that it is around 65 °C. Alternative HPA cooling solutions must have a transistor base temperature below 65 °C. The concepts evaluated for the design of the alternative HPA cooling solution include water cooled cold plate, heat pipes, bent thermosyphon and closed loop thermosyphon designs. The water cooled cold plate design was rejected, while the heat pipe design was not feasible. After applying the thermal management design process methodology to the bent thermosyphon and closed loop thermosyphon designs, the only unknown parameters for the designs were the thermal resistance and maximum heat transfer rate for each thermosyphon. The required energy could not be transferred by a single bent thermosyphon. Three closed loop thermosyphons with different diameters (Y.." , %" and Yz" outside diameter pipes) were tested using three different working fluids (R 134a, butane and water) with different fill ratios. The recommended alternative HPA cooling solution uses a single Yz" water filled closed loop thermosyphon. Depending on the cooling fluid temperature, flow rate and cold plate design, the alternative HPA cooling solution can achieve a transistor base temperature of 65 °C. It is concluded that the thermal management design process methodology must be implemented from the start of the design process so that the thermally associated risk of the product would have been significantly reduced, if not eliminated.

AFRIKAANSE OPSOMMING: Die termise probleme van die ESR 220 radar stelsel (Kameelperd) was ondersoek. 'n Termiese bestuur ontwerp proses metodologie was ontwikkel om hierdie en ander potentieele termiese probleme aan te spreek. Die HPA is gelee binne in die radar toerusting houer (REC). Die transistors in die hoe krag versterker (HPA) faal as gevolg van termiese skok en buitensporige hoe temperature wanneer die sisteem houer se lugtemperatuur hoog is. Die enigste manier om te verseker dat die transistors nie oorverhit nie, is om die lugtemperatuur van die sisteemhouer onverdraaglik laag te maak vir die operateurs. As die waaiers in die digitale sein verwerker (DSP) afgeskakel word oorskry die vier verwerker borde in die DSP die gespesifieseerde/aangewese temperatuur. Die termiese bestuur ontwerp proses metodologie was gebruik om die IKameelperd te analiseer. Die resultaat het aangedui dat die lugvloei in die REC en die bestaande HPA verkoeling metode geanaliseer moet word. Alternatiewe verkoelings metodes moet ondersoek word as 'n vervangings moontlikheid vir die bestaande HPA verkoelingsmetode. Flomerics FLOTHERM CFO program was gebruik om die lugvloei deur die REC te analiseer. Die analise het aangedui dat die posisionering en konfigurasie van die eenhede ontoepaslik was en dat dit nie slegs die lugvloei deur die REC beperk nie, maar ook die verspreiding van lug deur die DSP verwerkers verhinder. Daar word voorgestel dat die 'receiver front end' en die 'driver amplifier' her-ontwerp moet word. Daar word ook voorgestel dat die 'positioner interface' verwyder word en die 'EMI shield' verwyder of her-ontwerp moet word. Die voorgestelde veranderinge sal die lugvloei snelheid en die lugverspeiding verbeter. As die voorgestelde veranderinge aan die REC aangewend word dan moet lugvloei uitlaat konfigurasie van die sisteem houer verander word. 'n Numerise model, gebaseer op die eksperimentele data vir die bestaande HPA verkoelingsmetode, was gebruik om die transistor basis temperatuur te bereken en dit is bepaal dat dit om en by 65 °C is. Die alternatiewe verkoelings metodes moet dan verseker dat die transistor basis temperatuur ender 65 °C bly. Die konsepte wat ge-evalueer was vir die ontwerp van die alternatiewe HPA verkoelingsmetode, sluit in, water-verkoelings plaat, 'heat pipe', gebuigde 'thermosyphon', geslote lus 'thermosyphon'ontwerpe. Die water-verkoelings plaat ontwerp was verwerp terwyl die 'heat pipe'ontwerp nie uitvoerbaar was nie. Die enigste onbekende parameter vir die gebuigde 'thermosyphon' en die geslote lus 'thermosyphon' ontwerpe was die termiese weerstand en maksimum hitte oordrag vir elke 'thermosyphon'. Die gebuigde 'thermosyphon' kon nie die benodigde energie oordra nie. Orie geslote lus 'thermosyphon' met verskillende deursnitte (~". %"en %" buite deursnitte) was getoets met drie verskillende vloeistowwe (R134a, butane en water) met verskillende vullings ratios. Die voorgestelde alternatiewe HPA verkoelingsmetode gebruik 'n enkele %" water gevulde geslote lus 'thermosyphon'. Afhangend van die verkoelings vloeistof temperatuur, vloeisnelheid en verkoelingsplaat ontwerp, kan die alternatiewe HPA verkoelings metode 'n transistor basis temperatuur van minder as 65 °C behaal. Daar is dus tot 'n gevolgtrekking gekom dat die termiese bestuur ontwerp proses metodologie, vanaf die aanvang van die ontwerp proses geimplementeer moet word, sodat die termiese risiko verbonde aan die produk aansienlik verminder of elimineer word.

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