Thermohydrodynamic Characteristics Research Articles

The influence of installation deviation on the upper guide bearing thermo-hydrodynamic characteristics of a 1000 MW giant hydropower unit

The influence of installation deviation on the upper guide bearing thermo-hydrodynamic characteristics of a 1000 MW giant hydropower unit

Study on the startup-shutdown performance of gas foil bearings-rotor system in proton exchange membrane fuel cells

The startup-shutdown behavior of the gas foil bearings-rotor system is vital for proton exchange membrane fuel cells due to the inherently frequent start-stop of hydrogen fuel cell vehicles, which significantly affects the sustainable power generation and efficiency of the fuel cells. In this paper, the effects of three systematic factors including bump foil structure, nominal clearance, and coating on the dynamic response of the bearings-rotor system are first investigated based on startup-shutdown experiments. The mathematical model considering both gas film and thermo-hydrodynamic characteristics is presented to investigate the startup-shutdown behavior further. The influencing mechanisms of the factors on performance are analyzed. The energetic results demonstrate that the bearing structure parameters have a significant influence on the startup-shutdown performance and energy consumption. Considering optimal startup-shutdown performance, a better bearings-rotor system is proposed. Compared to the average values in all cases, the take-off speed, temperature rise, and average energy consumption of the system are decreased by 51.3%, 16.2%, and 60.7%, respectively. This indicates that the startup-shutdown improvement of the bearing-rotor system has great significance for enhancing the energy efficiency of the fuel cell.

Operating mechanism of pulsating heat pipe with different wettability from the perspective of thermo-hydrodynamic characteristics of vapor–liquid interface region

Pulsating heat pipe (PHP) is considered to be one of the most promising efficient heat sinks in electronic thermal management for good cooling capacity and compact structure. Understanding the complex operating mechanism of PHP from various angles is crucial for advancing its large-scale application. Among various factors, the thermo-hydrodynamic characteristics of the vapor–liquid interface region have a critical impact on the operation of PHP. Based on this, the transient numerical simulations were conducted in this work on PHPs with 20° and 150° contact angles (hydrophilic and hydrophobic, respectively), and the influence of different thermo-hydrodynamic characteristics of the vapor–liquid interface region on the operating mechanism of PHPs was analyzed. The results found that the presence of a widely spreading liquid film at the interface of hydrophilic PHP significantly changed its thermo-hydrodynamic characteristics compared to hydrophobic PHP. As a consequence, the hydrophilic PHP and hydrophobic PHP presented better heat transfer performance in the evaporation section and condensation section, respectively. Under low heat inputs, with regular vapor–liquid distribution in the interface region, the hydrophobic PHP presented better startup and heat transfer performance due to better hydrodynamic behavior caused by more easily formed pressure gradients. Under high heat inputs, the hydrophilic PHP showed significantly better heat transfer performance due to the intense evaporation and continuous spreading of new liquid film in the interface region, which also played a key role in stronger anti-dry-out performance.

Numerical Assessment of Advanced Thermo-Hydrodynamic Characteristics of Nanofluid Inside a Helically Featured Straight Pipe

This research set out to look at the aspects of flow and convective heat transfer in this novel geometry for helically corrugated pipes. The main goal is to evaluate the thermo-hydrodynamic performance of single and hybrid nanofluids in this modified shape at various Reynolds numbers and densities of nanoparticles. With dimensional modifications, such as helical pitch and corrugation shape at the inlet, different case studies were performed for comparison in heat exchanger performance. The simulations were conducted using the ANSYS commercial program, employing the Realizable k-epsilon turbulence model. A uniform heat flux of 1000 W/m2 was assumed, and the Reynolds numbers ranged from 5000 to 20,000. The study makes use of computational techniques to evaluate the thermo-hydrodynamic capabilities of corrugation coupled with varying volume fractions (1–5 %) of single-phase nanofluids (Al2O3 and CuO) and hybrid nanofluid (1 % Al2O3/Cu) where water is kept as the conventional base fluid. The second-order upwind technique is applied for solution approximation and discretization with SIMPLE pressure-velocity coupling. Within the collection of case studies, it was observed that the most significant enhancement occurred when there was a modification in the shape of the corrugation inlet. Additionally, concerning the corrugation pitch, it was found that the tube with the smallest pitch exhibited notably improved performance. Due to the intricacy of these corrugations, which enhances heat transmission and pressure drop, a higher Nusselt number results. The heat transfer coefficient for various nanoparticle compositions for the helically corrugated pipe is demonstrated to be 20–30 % greater than for the smooth pipe. Considering the pressure drop penalty and heat transfer increment in terms of performance evaluation criterion (PEC), the 1 % Al2O3/Cu water hybrid nanofluid has been found to be the best-acquitted working fluid in the corrugated pipe flow with a maximum thermal performance improvement of 26.5 %. The study also shows that the gain in thermal efficiency steadily declined with increasing Re but increased as the nanofluid's volume concentration climbed.

Flow and thermo-hydrodynamic characteristics in supercritical CO2 lubrication

Supercritical CO2 is used as an important lubricant in Brayton cycle turbomachinery, and the study of lubricant flow and heat transfer mechanisms plays a crucial role in the lubrication performance of Supercritical CO2. To improve the thermal environment and load capacity performance of lubrication in turbomachinery, the turbulence models and real gas models were used in this work to numerically simulate the evolution of lubrication flow and thermal characteristics of CO2 from low pressure to supercritical condition. Simulations were conducted under various operating parameters and lubrication conditions. The rarefaction effect, viscous heat, compression heat and tribological performance were analyzed. The findings indicate that the lubrication film temperature characteristics of low operating pressure depended on the viscous heat dissipation. Under the effect of rarefaction, the CO2 lubrication pressure maximum decreased of 3.0 %. As the operating pressure increased to the supercritical condition, the compression heat effect of SCO2 lubricating film increased and dominated the temperature distribution characteristics of the lubricating film. High operating pressure enhanced the pressure and load capacity of the lubrication film, and reduced the maximum lubrication temperature by 7.2 K. However, it was observed that near the critical temperature, fluctuations in the load capacity and friction torque of the lubricating film damaged the stable operation of the rotor. The change in lubrication film thickness has a significant impact on the load capacity and viscous heat dissipation, with variations as high as 81.4 % and 82.6 %, respectively. The research results provide guidance for the selection of operating pressure and temperature within the lubrication film, thereby improving the thermal working environment and operational stability of the rotor and stator.

Investigation of thermo-hydrodynamic characteristics in micro-oscillating heat pipe by alternatively-arranged ratchet microchannels

In this study, three flat-plate micro-oscillating heat pipes (FPMOHPs) with different alternatively-arranged ratchet microchannels were designed and fabricated. Then, a combined visualization and thermal experiment was conducted to examine the regulation of thermo-hydrodynamic characteristics in the FPMOHPs by the alternatively-arranged ratchet microchannels, via the comparison with a traditional FPMOHP with completely uniform microchannel. The detailed fluid flow motions and corresponding temperature oscillations as well as thermal performance of the FPMOHPs were illustrated and analyzed to clarify the advantages of this microchannel design. It is indicated that the oscillating frequency and velocity of the fluid are diminished by the ratchet microchannels because of the higher flowing resistance. However, the ratchet microchannels can trigger the stronger flow disturbance, leading to the ascending “wave-like” annular flow broken into the dispersive slugs or bubbles with irregular shape. Among the three different ratchet microchannels, the asymmetric ratchet structure with the larger contraction-expansion ratio near the inlet of the fluid can trigger more intense boiling in the evaporator, which also energizes the downward flow from the condenser. Furthermore, the additional actions on the bubbles/slugs caused by the Laplace pressure jump in three different ratchet microchannels play distinct roles in upward and downward bubble/slug flow, i.e., driving force or resistance force or little role, which determine the most favorable ratchet structure for the fluid flow and heat transfer in the FPMOHPs. In general, the positive effects of the enhanced boiling and the stronger fluid flow disturbance caused by the ratchet microchannel dominates the negative effect of growing flow resistance, leading to the enhanced convective heat transfer. Therefore, the equivalent thermal conductivity can be improved up to 33.8 % on average as compared to the traditional FPMOHP with completely uniform rectangular channel.

Bifurcation analysis of combined double-diffusive natural convection and thermal radiation under a non-uniform magnetic field in a wavy enclosure

In the current work, the bifurcation phenomenon of a double-diffusive natural convection flow is analyzed for a non-uniform magnetic field applied to a wavy enclosure in the presence of radiation, for the first time. The finite volume method has been utilized to simulate volumetric radiation. To solve the continuity, momentum, energy, and species equations, the multiple-time relaxation lattice Boltzmann technique is adopted. In addition, the immersed boundary approach has been applied to identify the complex boundaries inside the Cartesian coordinates system. The effects of specific pertinent parameters, including the optical thickness (0.1≤τ≤100), Buoyancy ratio (-5≤N≤5), Rayleigh number (104≤Ra≤105), wave amplitude (0≤λ≤0.2), and Hartmann number (0≤Ha≤50) on thermohydrodynamic characteristics of the system have been investigated. The results indicated that an increase in Hartmann number disappears the bifurcation phenomenon. In addition, it was observed that the initial condition of hot temperature and high concentration leads to instability in the flow. In the radiation case for λ>0.1, 5<τ<30, and 15≤Ha≤30, the flow appears unsteady. Bifurcation occurs in all values of wavy amplitude, and optical thickness studied. Heat and mass transfers decrease when the initial condition is cold temperature and low concentration. Also, Radiation does not affect the critical Rayleigh number.

Comprehensive assessment of the partially-saturated-cells framework for convective problems

We present a comprehensive investigation of Partially-Saturated-Cells method (PSC) for the simulations of incompressible thermal flows. The methodology comprises an additional collision operator introduced into the conventional simplified thermal lattice-Boltzmann (STLBM) method that offers a unified evolution equation for solid and fluid media present in the computational domain. It is a type of diffuse-interface immersed-boundary method that is dictated by the volume fraction of the solid medium and facilitates a smooth transition of boundary conditions at the solid-fluid interface. In this work, we devise a mechanism to evaluate local heat flux at the solid-fluid interface and present its congruity with several heat transfer problems. We also derive the recovery of the macroscopic energy equation from PSC's evolution equation through Chapman-Enskog multiscale expansion. Our investigation also reveals that the method is first-order accurate for moving body simulations irrespective of the straight or curved boundary. It is also Galilean invariant and demonstrates identical heat transfer characteristics in stationary and moving reference frames. A comprehensive analysis of the PSC algorithm is presented to enlighten its suitability for predicting thermo-hydrodynamic characteristics in free, forced, and mixed convection phenomena involving both stationary and moving boundary scenarios. To the best of our knowledge, these aspects pertaining to PSC methodology have not been discussed in the literature so far.

Investigation on the influence of different heat transmission distances on thermo-hydrodynamic characteristics of pulsating heat pipes

Pulsating heat pipe (PHP) exhibits potential as a high-heat-flux heat sink in various thermal applications. It is crucial to understand the impact of heat transmission distance on the thermo-hydrodynamic characteristics of PHP since the heat transmission distance differs in various applications. In this paper, the start-up, flow, and heat transfer performance and anti-dry-out capacity of PHPs with different heat transmission distances (130 mm, 500 mm, 1000 mm, and 1500 mm) were experimentally investigated. The experimental results indicated that at low heat input, the start-up performance of the PHP deteriorated significantly as the heat transmission distance increased. The peak temperature of the evaporation section (Ts, max) was high and the start-up time was long for the PHP with a long heat transmission distance. As the heat transmission distance grew, the flow performance of the PHP also deteriorated, and more heat was needed to convert the flow regime from oscillation at intervals to oscillation without stagnation. The thermal resistance increased significantly with the growth of the heat transmission distance at the range of 5 W–50 W, while the thermal resistances under different heat transmission distances were close at the range of 60–100 W. As the heat transmission distance grew, the anti-dry-out capacity initially rose and subsequently fell. So there was an optimal heat transmission distance that made the PHP have the finest anti-dry-out capacity. What’s more, the heat transmission distance of 1500 mm was approximately equal to the limit heat transmission distance for the PHP in this work.

Experimental study on the thermo-hydrodynamic characteristics of a nitrogen pulsating heat pipe

A simultaneous thermal and visual experiment is conducted on a silicon-based flat-plate nitrogen pulsating heat pipe (PHP) for the first time. The PHP operates successfully with six filling ratios (FRs) between 25% ∼ 76% under bottom heating mode. Start-up and quasi-steady state performances are analyzed. Two types of start-up processes induced by bubble nucleation and interface evaporation are observed, and different start-up mode results in different degrees of thermal performance hysteresis phenomenon. The optimal thermal resistance with different FRs is always lower in a lower FR working condition, but a lower FR results in a lower heat transfer limit. The optimal FR rises with increasing heat load range. The fluid flow data are quantified in two aspects, which are flow intensity and velocity, and coupled with the heat transfer data for analysis. It is inferred that the latent heat transfer efficiency in the nitrogen PHP is higher than that of the sensible heat transfer.

Thermo-hydrodynamic characteristics and entropy generation in a tube heat exchanger using multiple head ribbed geometries

Heat exchangers are critical components in a wide range of industries, and optimizing their thermal performance remains an important research area. To augment the thermal efficiency in a heat exchanger, several investigations have been done to increase the wetted surface area using a rib profile. Still, there exists a lack of research attempts to change the geometrical shape, such as multiple-head ribbed geometry with coil revolution in a straight heat exchanger. Therefore, the present study takes a numerical approach to examine the effect of multiple ribbed geometries, considering the variable coil revolution of the rib profile in a straight-type heat exchanger. The study was initially validated from two experimental correlations and previous numerical work. Three rib surfaces (2 ribs, 3 ribs and 4 ribs) and three different coil revolutions (10 revolutions, 20 revolutions and 30 revolutions) were taken into consideration to make nine configurations. Air was used as fluid under heating conditions. The results have been represented in terms of velocity, temperature profiles, local Nusselt number (Nu), pressure drop, friction factors and entropy generations for all the configurations. A significant enhancement in heat transfer was found when the rib head number is lesser, whereas the coil revolution number is higher. Consequently, the highest Nusselt number (Nu) was observed in the configuration of 2 ribbed 30 revolutions, and the lowest was found in 4 ribbed 10 revolutions. Furthermore, the friction factor rises because of higher coil revolution for a specific rib head number. It is found that in four rib head geometry, the friction factor rises 2 times when the revolution number is 30 than the case of revolution number 10. It is also observed that the 4 rib head 10 revolution configurations provides the lowest entropy generations among the configurations. Thus, the study suggests choosing the right configuration to design a straight heat exchanger with ribbed head profile to get the highest thermal performance. Following this study, these design modifications can be applied to other types of heat exchangers as well.

Thermo-hydrodynamic performance of tubular pulsating heat pipes with integral sintered powder wicks

The untraditional copper tubular pulsating heat pipes with integral inner-wall sintered powder wicks (PHPWWs) were fabricated to improve the thermal performance of the traditional pulsating heat pipes with no wicks (PHPWNWs). An experiment was performed to investigate the start-up and quasi-steady thermo-hydrodynamic characteristics of the PHPWWs and compare them with the PHPWNWs. The results indicate that, the wicks can improve the nucleation boiling in the evaporator to enhance the thermal driving force and provide additional capillary action to facilitate the liquid backflow to the evaporator. Consequently, differing from the PHPWNWs, the PHPWWs are able to work at the horizontal orientation, and their internal fluid flow motions ‘abnormally’ become smoother with decreasing inclination angle from 90° to 0°. In addition, PHPWWs has the lower start-up and quasi-steady-operation evaporator temperature as well as better thermal performance and gravity adaptability when compared with the PHPWNWs with similar inner and outer tube diameter. The operating principle of the PHPWW, especially the driving principle of the internal fluid, is determined by the cooperation and competition between those of the traditional PHPWNW and the conventional sintered wick heat pipe, which is affected by the inclination angle and particularly the tube inner diameter.

Thermo-Hydrodynamic Analysis of Low-Temperature Supercritical Helium Spiral-Grooved Face Seals: Large Ambient Temperature Gradient

Hhighly efficient and reliable sealing technology is essential to improve the efficiency of precooled aeroengines. To explore the effects of large ambient temperature gradients on the sealing performance, the thermo-hydrodynamic characteristics of a supercritical helium spiral-grooved face seal were studied numerically, under low-temperature conditions. Considering the real gas effect of helium, the thermal deformations of the seal were analyzed numerically, under different temperature gradients. Additionally, the distributions of the pressure, temperature, and film thickness of the gas film were calculated, and the sealing performances of the seal under a wide range of working conditions were evaluated simultaneously. Results showed that a turning point occurred at the sealing pressure of 1.6 MPa in both the dynamic pressure effect and temperature rise of the gas film under the ambient-temperature gradient, leading to the transformation of the sealing gap, from convergent to divergent. The temperature gradient contributed to decreasing the thermal deformation and improving the sealing performance of the face seal. As the temperature gradient increased, although a mutational phenomenon existed near the sealing temperature of 250 K with both the dynamic pressure effect and the temperature rise, the variation of the opening force was within 120 N and the leakage was more than halved, indicating the broad application prospects of gas face seals in precooled aeroengine systems.

Analysis of functionally graded metal foams for the accomplishment of heat transfer enhancement under partially filled condition in a heat exchanger

The use of partially filled high porosity graded aluminum and copper foams is explored to satisfy both heat transfer and pressure drop in a heat exchanger. Both positive and negative orientations are accomplished for the enhancement of heat transfer with reduction in the pressure drop. The present research includes three different configurations M1, M2 and M3 (porous layer inner diameter = 0.06 m, 0.04 m, and 0.02 m, respectively, while outer diameter = 0.10 m) partially filled with positive (i.e., increasing, 20/45 PPI) negative (i.e., decreasing, 45/20 PPI) and compound (i.e., 45 Cu/20 Al PPI) graded porous layer thickness. Each configuration involves three different graded porous layer to present the optimum graded porous layer thickness. The thermo-hydrodynamic characteristics are apprehended by using Darcy Extended Forchheimer (DEF) flow and local thermal non-equilibrium (LTNE) models for the partially filled graded porous structure and k-ω turbulence model is accomplished in open passage flow of the conduit. The decreasing graded foam located inside the models M1 and M2 performed 1.68%–12.85% and 13.42%–23.32% higher heat transfer rate compared to without graded metal foam of models M2 and M3, respectively accompanied with 55.43%–84.02% and 35.69%–50.31% lesser pumping power.

Effect of different corrugation interruptions Parameters on thermohydrodynamic characteristics and heat transfer performance of 3D Three-dimensional corrugated tube

The use og internal corrugated tubes with varying Reynolds numbers (Re) at a constant wall heat flux, we examine the effects of mixing secondary, spiral, and swirl flows on heat transfer and pressure drop. Furthermore, varying flow analysis is applied to examine the flow resistance, heat transfer, and other design parameters. Our research indicates that heat transfer enhancement can be attributed to two factors. First In corrugated configurations, convective heat transfer is transformed into jet impingement heat transfer. Second, the boundary layer on the leeside of the corrugation was dramatically redeveloped by pulsation. Heat transfer performance is significantly improved and pressure drop is increased due to the spiral flow. Additionally, different corrugated geometrical configurations are used to investigate the flow behaviour based on Nusselt numbers (Nu) and friction coefficients (f) corresponding to the analyse values, and the design parameters such as corrugated ring angle (CRA), corrugated ring diameter (CRD), and a corrugated ring number (NCR). The result indicates that the Nu tend to increase as increases of the Re. The Nu value increases at higher corrugated geometrical configurations increase. Using different corrugated geometric configurations can result in performance superior to smooth pipes because the performance evaluation factor (PEF) value is higher than unity. Both PEF and Re increments, as well as the PEF value, demonstrate a reducing trend.

Investigation on magnetic force and buoyancy force on flow and heat transfer of Al2O3-water nanofluid at various temperature-dependent thermophysical models by a novel PLBM

A novel preconditioned lattice Boltzmann method (PLBM) is applied to investigate the thermo-hydrodynamic characteristics of Al2O3-water nanofluid with various temperature-dependent thermophysical properties and slip boundary conditions in a microchannel. Also, the effects of a magnetic field force, buoyancy force, and volume fraction of nanoparticles are analyzed, respectively. The theoretical level confirms that the convergence performance of the PLBM is greatly improved at large Reynolds numbers compared to the original LBM. Numerical results show that the Koo & Kleinstreuer model has the largest average shear stress and average Nusselt number. Among all the physical models considered, these two values are approximately 1.05 times and 1.2 times of the values by the Maxwell & Brinkmann model, respectively. Once the magnetic field is considered, the average shear stress is increased twice and the average Nusselt number increases by about 10% and further by about 20% at higher buoyancy forces. The growth of these two values gradually slows down when the volume fraction of nanoparticles exceeds 2%. The heat transfer process makes the largest contribution to entropy generation when the magnetic field force is not considered. Accordingly, it will dominate the irreversible loss due to the strong shear stress once the magnetic field force is involved in the heat transfer process.

Thermal performance of a tandem-dual-channel flat-plate pulsating heat pipe applicable to hypergravity

Thermo-hydrodynamic characteristics of a novel flat-plate pulsating heat pipe (FP-PHP) with a symmetrically tandem dual-serpentine-channel were studied experimentally under the simulated hypergravity by a rotating platform capable of providing an adjustable centrifugal acceleration up to a = 4 g0 (g0 = 9.8 m/s2) on ground. The influences of gravity level, heat load, and orientation (i.e., circumferential orientation (C-O) and radial orientation (R-O)) on thermo-hydrodynamic performance of the FP-PHP were investigated. It is indicated that, similar to the traditional single-serpentine PHPs under the normal gravity, the quasi-steady flow motion in the FP-PHP under the hypergravity could be also classified into five flow patterns, i.e., stop-over, intermittent pulsation, pulsation, pulsation with circulation and circulation. Increasing hypergravity level is not conducive to the start-up process of the FP-PHP, which needs larger start-up heat load and higher start-up temperature. Even so, under a ≤ 4 g0, the FP-PHP can successfully start up within decent temperature level of 58 °C. Growing hypergravity level induces increasing negative influences on the thermo-hydrodynamic performance of the FP-PHP, which is more obvious under the R-O than that under the C-O. Anyway, in general, FP-PHP possesses a good thermal performance uniformity, which has an average coefficients of variation less than 3% in thermal resistance of its two symmetric halves. In addition, FP-PHP has an average equivalent thermal conductivity 4.38 times that of the pure 6063 aluminum alloy plate and a total weight 83.6% of it. The average equivalent thermal conductivity ratio of the FP-PHP under the hypergravity of a ≤ 4 g0 to that under the normal gravity is not smaller than 0.70, indicating a good adaptability of the FP-PHP to hypergravity. Accordingly, the FP-PHP could be regarded as a promising option for modern avionics passive thermal control systems for multiple heat sources.

The Influence of Varying Corrugation Interruptions Configurations on Thermohydrodynamic Characteristics and Enhancement of Heat Performance of 3D Corrugated Pipe

The Influence of Varying Corrugation Interruptions Configurations on Thermohydrodynamic Characteristics and Enhancement of Heat Performance of 3D Corrugated Pipe

Investigation of the Tribological Performance of Heterogeneous Slip/No-Slip Journal Bearing Considering Thermo-Hydrodynamic Effects

The slip boundary has an important influence on hydrodynamic journal bearing. However, less attention has been paid to the positive effect of slip on thermal behaviour. In this study, a computational fluid dynamics (CFD) analysis investigating the thermo-hydrodynamic (THD) characteristics of heterogeneous slip/no-slip bearings running under steady, incompressible, and turbulent conditions is presented. A comprehensive analysis is made to investigate the THD behaviours of heterogeneous slip/no-slip bearings in terms of lubricant pressure, temperature distribution, volume fraction of vapor, and load-carrying capacity when they are running under different shaft rotational speeds. The multiphase cavitation model is adopted to represent the real operational condition of the journal bearing. Numerical results show that the load-carrying capacity of the heterogeneous slip/no-slip bearing can be significantly increased by up to 100% depending on the rotational speed. It is also observed that there is an optimal journal rotational speed for maximizing the load-carrying capacity. An insightful new finding is revealed in a numerical framework, wherein it is found that by introducing the heterogeneous slip/no-slip pattern, the maximum temperature can be reduced by up to 25% in comparison with a conventional bearing.

Engineering Calculation and Experimental Study of a Cone-Shaped Coil Heat Exchanger

To improve the characteristics of heat and power equipment, it is necessary to develop new designs of heat exchangers, increase the efficiency of heat exchange surfaces, apply modern approaches to the design and calculation of heat exchangers, and create new technologies for their production. The paper proposes modern compact coil heat exchangers of the in pipe type with a variable bending radius of the helical spiral and the engineering method calculating the thermohydrodynamic characteristics of such devices. The calculation of a coilheat exchanger with a linearly varying bending radius of a helical spiral (cone-shaped coil heat exchanger) has been performed. They performed the experimental study of heat transfer in a cone-shaped coil heat exchanger of the pipe-in-pipe type. They obtained the empirical formulas for the Nusselt number and hydraulic resistance coefficient. It has been established and experimentally confirmed that cone-shaped coil heat exchangers are morecompact and efficient in comparison with the known cylindrical coils. It is proposed to modernize the hot water preparation unit in one of the residential buildings in the city of Kazan (Russia) by replacing the outdated shelland-tube heat exchanger with a compact cone-shaped coil heat exchanger, which made it possible to reduce the duration of hot water preparation significantly, to reduce the costs of the heating medium and, thus, to reduceconsumer costs.