【導讀】基于MSP430的溫度采集報警系統的畢業(yè)論文基于單片。溫度控制儀表具有廣泛的應用前景在各種行業(yè)中都占有重要的位置越來越。多的領域應用到以單片機為控制核心用液晶作為顯示終端的數字化控制設備通。過單片機對被控對象進行智能控制。本設計是從降低開發(fā)成本擴大適用范圍系統運行的穩(wěn)定性可靠性的設計目。的出發(fā)采用MSP430F149單片機為控制核心以單線數字溫度傳感器DS18B20來完。成溫度信號的采集溫度以數字的方式顯示在LCD1602液晶上最終實現溫度的采。集顯示和報警上下限溫度值可以根據實際要求通過鍵盤輸入來實現設定從而實。中硬件構成有六部分電源及復位模塊采集模塊鍵盤輸入模塊顯示模塊和報警模。MSP430F149是一種16位內含FLASH型芯片的單片機具有高速運算開發(fā)設備。路原理圖都有protel來完成每個模塊的軟件編程都在IAR開發(fā)環(huán)境中完成并實?？梢赃_到01℃該傳感器測量精度高互換性好等優(yōu)點筆者可以在DS18B20的程序。中設定一個溫度域若所顯示的溫度超出所設定溫度的上下線時報警

　　

【正文】 rottled to the evaporator pressure by an expansion device such as a thermostatic expansion valve The sink for sub cooling the liquid is low temperature refrigerant vapor leaving the evaporator Thus the liquidsuction heat exchanger is an indirect liquidtovapor heat transfer device The vaporside of the heat exchanger between the evaporator outlet and the pressor suction is often configured to serve as an accumulator thereby further minimizing the risk of liquid refrigerant carryingover to the pressor suction In cases where the evaporator allows liquid carryover the accumulator portion of the heat exchanger will trap and over time vaporize the liquid carryover by absorbing heat during the process of sub cooling highside liquid Background Stoecker and Walukas 1981 focused on the influence of liquidsuction heat exchangers in both single temperature evaporator and dual temperature evaporator systems utilizing refrigerant mixtures Their analysis indicated that liquidsuction heat exchangers yielded greater performance improvements when nonazeotropic mixtures were used pared With systems utilizing single ponent refrigerants or azeoptropic mixtures McLinden 1990 used the principle of corresponding states to evaluate the anticipated effects of new refrigerants He showed that the performance of a system using a liquidsuction heat exchanger increases as the ideal gas specific heat related to the molecular plexity of the refrigerant increases Domanski and Didion 1993 evaluated the performance of nine alternatives to R22 including the impact of liquidsuction heat exchangers Domanski et al 1994 later extended the analysis by evaluating the influence of liquidsuction heat exchangers installed in vapor pression refrigeration systems considering 29 different refrigerants in a theoretical analysis Bivens et al 1994 evaluated a proposed mixture to substitute for R22 in air conditioners and heat pumps Their analysis indicated a 67 improvement for the alternative refrigerant system when system modifications included a liquidsuction heat exchanger and counter low system heat exchangers evaporator and condenser Bittle et al 1995a conducted an experimental evaluation of a liquidsuction heat exchanger applied in a domestic refrigerator using R152a The authors pared the system performance With that of a traditional R12based system Bittle et al 1995b also pared the ASHRAE method for predicting capillary tube performance including the effects of liquidsuction heat exchangers with experimental data Predicted capillary tube mass flow rates were within 10 of predicted values and sub cooling levels Were Within 17C 3F of actual measurements This paper analyzes the liquidsuction heat exchanger to quantify its impact on system capacity and performance expressed in terms of a system coefficient of performance COP The influence of liquidsuction heat exchanger size over a range of operating conditions evaporating and condensing is illustrated and quantified using a number of alternative refrigerants Refrigerants included in the present analysis are R507A R404A R600 R290 R134a R407C R410A R12 R22 R32 and R717 This paper extends the results presented in previous studies in that it considers neW refrigerants it specifically considers the effects of the pressure dropsand it presents general relations for estimating the effect of liquidsuction heat exchangers for any refrigerant Heat Exchanger Effectiveness The ability of a liquidsuction heat exchanger to transfer energy from the Warm liquid to the cool vapor at steadystate conditions is dependent on the size and configuration of the heat transfer device The liquidsuction heat exchanger performance expressed in terms of an effectiveness is a parameter in the nalysis The effectiveness of the liquidsuction heat exchanger is defined in equation 1 1 Where the numeric subscripted temperature T values correspond to locations depicted in Figure 1 The effective enessis the ratio of the actual to imum possible heat transfer rates It is related to the surface area of the heat exchangerAzero surface area represents a system With out aliquidsuction heat exchanger Whereas a system having an infinite heat exchanger area corresponds to an The liquidsuction heat exchanger effects the performance of a refrigeration system by in fluencing both the high and low pressure sides of a system Figure 2 shows the key state points for a vapor pression cycle utilizing an idealized liquidsuction heat exchanger on a pressureenthalpy diagram The enthalpy of the refrigerant leaving the condenser state 3 is decreased prior to entering the expansion device state 4 by rejecting energy to the vapor refrigerant leaving the evaporator state 1 prior to entering the pressor state 2 Pressure losses are not shown The cooling of the condensate that occurs on the high pressure side serves to increase the refrigeration capacity and reduce the likelihood of liquid refrigerant flashing prior to reaching the expansion device On the low pressure side the liquidsuction heat exchanger increases the temperature of the vapor entering the pressor and reduces the refrigerant pressure both of which increase the specific volume of the refrigerant and thereby decrease the mass flow rate and capacity A major benefit of the liquidsuction heat exchanger is that it reduces the possibility of liquid carryover from the evaporator which could harm the pressor Liquid carryover can be readily caused by a number of factors that may include Wide fluctuations in evaporator load and poorly maintained expansion devices especially problematic for thermostatic expansion valves used in ammonia service 冷卻系統利用流 體吸熱交換器 加熱裝置在許多冷卻系統中被用到用以制冷時