Research On Threaded Pipe Heat Exchanger For Refrigerating Mud

In the gas hydrate sampling drilling, because of the special low temperature and highpressure occurrence state of hydrate, temperature of the circulation of the drilling fluid mustbe strictly controlled, inhibiting hydrate decomposition occurring in the drilling process.Currently, the core component heat exchanger of the mud cooling system in gas hydratedrilling, which is developed by our school, uses the coaxial pipe heat exchanger, whose innerand outer pipe both are smooth pipes. This pipe has many unique advantages, but inconsideration of the heat transfer efficiency, the smooth pipe heat transfer efficiency is notthe highest, so we make improved optimization on the basis of the existing mud refrigerationsystem. Inner pipe of the coaxial casing heat exchanger is threaded pipe, which is an highefficiency heat exchange pipe once squeezed out by unit in the steel or stainless steel tube,strengthening its role out of the pipe, on the one hand, the thread increases the heat transferarea, while on the other hand,the surface thread divides the boundary layer of the laminarflow when then aqueous solution of ethylene glycol flows through the annulus threaded tubesurface, thinning the thickness of the boundary layer, turbulent flow more easily coming into,and also surface turbulence stronger than the smooth pipe, further thinning the boundarylayer thickness. According to the relevant knowledge of heat transfer, fluid mechanics andheat exchangers, heat exchanger design calculations has been carried out.Using SolidWorkssoftware to establish a three-dimensional model of the threaded pipe heat exchanger, usingfluid analysis software SolidWorks Flow Simulation to make numerical simulations forthreaded pipe heat exchanger; verifying the results of theoretical calculations with thenumerical simulations. From the results temperature contours of the numerical simulation canbe drawn: Under the conditions of theoretical calculations of the parameters, after the heatconvection of the mud and low temperature glycol in the threaded tube heat exchanger, thetemperature of the mud droppedfrom0℃to-2.07℃, numerical simulation results agreewith the theoretical calculations, verifying the reliability of the results of theoreticalcalculations. For further study of the mud cooling heat exchanger, such as research of the heattransfer performance of different types and the same kind of heat exchanger performance indifferent conditions, we designed the mud cooling device for gas hydrate drilling, andconducted equipment selection and building indoor test platform. Through the laboratory testdevice, we test the indoor mud cooling system and test the temperature and flow of the keypoints to understand the impact of flow, different types of heat exchangers on therefrigeration effective of the mud cooling.From the analysis of the laboratory test data of the threaded pipe mud cooling heatexchanger can be drawn: the threaded pipe mud cooling heat exchanger has higher heatexchange efficiency so that can meet the design requirements of the theory better, and it caneffectively reduce mud temperature to quickly reduce the temperature of the mud to0℃.We carried out field trials with the designed threaded pipe mud cooling heat exchangerby applying to Qiangtang Basin gas hydrate drilling test wells project to test the reliability ofthe threaded tubular mud cooling heat exchanger, and add antifreeze device in the originalmud refrigeration system to prevent the internal heat exchanger icing problems. We makeimproved optimization on the basis of the original mud refrigeration system, the refrigerationunit uses AC variable frequency start up, and integrate refrigerant tank, threaded tube heatexchangers, unit pumps, refrigerant pumps and paperless recorder into one box, which resultsto higher degree of automation and integration of the new mud refrigeration system. The newmud refrigeration system has been applied in gas hydrate drilling in the Muli Basin in theQilian region. Test results show that: threaded pipe heat exchanger can effectively reduce thetemperature of the mud so that meet the requirements of gas hydrate sampling drilling andachieve a good design expectation.