Two-phase Loop Thermosyphon Research Articles

Assessment of the two-phase thermosyphon loop with high filling ratio under anti-gravity

In various fields of thermal management and protection, such as vehicles, aircraft, and mobile electronic devices, it is crucial to transfer heat effectively from the top to the bottom. The use of a simple structure for this transfer can reduce the weight of the heat transfer system. Theoretical studies have demonstrated that the two-phase thermosyphon loop (TPTL) with a high filling ratio has the potential for excellent performance in anti-gravity applications. In this study, we investigate the thermal performance of a high filling ratio TPTL under anti-gravity conditions. Our results reveal that, contrary to previous understanding, a TPTL with a high filling ratio can effectively transfer heat in anti-gravity. However, we also found that the loop thermal resistance of TPTL under anti-gravity is greater than under gravity, and the heating surface temperature is higher. Additionally, we experimentally study the effect of inclination angles on anti-gravity performance, and our results indicate that smaller angles result in better heat transfer. Finally, we investigate the impact of cooling water temperature on thermal performance. Overall, considering the energy efficiency of the heat dissipation system and the heat transfer capacity of the device, it is not recommended to use cooling water at a lower temperature. This research sheds light on the potential for TPTLs to operate in anti-gravity conditions and supports their practical applications.

Experimental study of instability characteristics of a CO2 two-phase thermosyphon loop

During the operation of a two-phase thermosyphon loop (TPTL), instability often occurs and is accompanied by fluctuations in temperature, pressure, and mass flow rate, which can lead to premature failure and damage to components. To avoid instability of the TPTL, the mechanism should be understood. In this study, the instability characteristics and occurrence conditions of a CO2 TPTL were experimentally investigated. A distribution map of the different types of instability is provided. Geyser boiling occurs mainly at low heat loads and filling ratios. The flow pattern in the downcomer experienced period change of “violent bubbly flow- annular flow- fluctuating annular flow- violent bubbly flow.” Natural circulation oscillation was more likely to occur at medium filling ratios. The flow pattern in the downcomer experienced a variation of “single liquid phase- churn flow- bubbly flow- churn flow-bubbly flow- single liquid phase.” Density wave oscillation mainly occurred when the filling ratio was as high as 60% and 70%, and an unstable churn flow was observed in the riser. Generally, the fluctuation period decreased as the heat load increased, and the fluctuation amplitude tended to decrease at higher filling ratios.

CFD simulation on the operation characteristics of CO2 two-phase thermosyphon loop

The working fluid flow and vapor–liquid distribution in a CO2 two-phase thermosyphon loop (TPTL) can hardly be properly understood through experiment. In the present study, a two-dimensional computational fluid dynamics model of a CO2 TPTL was established and verified. The prestart, oscillatory, and stable operation states of the CO2 TPTL were reproduced and analyzed by simulation. The operating characteristics under different filling ratios were studied through inner parameters distribution and the heat transfer performance was compared. In the prestart operation stage, superheating was observed in the riser, and vapor–liquid reverse flow occurred in the downcomer, thus indicating an irregular flow in the loop. In the oscillatory operation stage, the operating parameters and flow pattern exhibited periodic variations. In the stable operation stage, the TPTL was operating in an adequate condition until it reached its heat transfer limit. When the filling ratio was too high or too low, premature single-phase heat exchange occurred in the TPTL. Superheating or subcooling in the TPTL led to high loop thermal resistance. Under a medium filling ratio, the thermal resistance was the lowest, and heat transfer limit was the highest. The heat transfer limit of the TPTL was approximately 1150 W.

Experimental study on the passive regulation of a CO2 two-phase thermosyphon loop

• The passive regulation mechanism of CO 2 TPTL was revealed. • Three typical operation states of the TPTL occurred as the heat load increased. • Each operation state showed different characteristics as the filling ratio changed. • The largest normal operation heat load range was found under 45% filling ratio. Vapor–liquid distribution and flow characteristics in a two-phase thermosyphon loop usually exhibit regular variation under varying working conditions, which can be referred to as passive regulation. Currently, the passive regulation law of a CO 2 two-phase thermosyphon loop has not been well understood. In this study, experiments were performed to examine the passive regulation mechanism of a CO 2 two-phase thermosyphon loop under different heat loads and filling ratios. Local flow visualization was adopted, combined with the measurement of operating parameters. The CO 2 two-phase thermosyphon loop entered the pre-start, oscillatory, and stable operation stages successively with the increase in heat load. Vapor–liquid counterflow was observed in the downcomer in the pre-start stage. Temperature change due to thermal unbalance between the vapor and liquid can be observed along the riser or the downcomer. In the oscillatory stage, different types of oscillation were observed under different filling ratios. In the stable stage, the two-phase thermosyphon loop worked under good conditions until the heat transfer limit was reached. The two-phase thermosyphon loop reached its maximum heat transfer limit of 1200 W at a filling ratio of 45%. The normal operation heat load range of the two-phase thermosyphon loop was 380–650 W, 320–770 W, 700–1100 W, 600–1200 W, and 400–630 W for filling ratios of 20%, 25%, 40%, 45%, and 50%, respectively.

Experimental investigation on the effect of vertical vibration on heat transfer performance of two-phase loop thermosyphons with different diameters

The two-phase loop thermosyphon (TPLT) is generally a technique used in conjunc?tion with a fan when cooling an electronic chip to enhance the cooling effect. In this context, the TPLT heat transfer efficiency is directly affected by the vibration caused by the associated fan. In this paper, the heat transfer performances of TPLT with diameters of 4 mm, 6 mm, and 8 mm were experimentally investigated under a heat?ing power capacity ranging from 40-400 W, a filling ratio of 40-70%, and a 30 m/s2 35 Hz vertical reciprocating vibration. The heat transfer performance of the TPLT is compared to the case of operation under the same working conditions in a static state. The influence of the vibration state caused by the fan rotation on the heat transfer performance of TPLT with different diameters is analyzed and discussed. The obtained results indicated that vertical vibration does not change the trend of TPLT heat transfer performance with the corresponding heating power capacity un?der each pipe diameter. On the other hand, it was found that the vibration enhances or inhibits the heat transfer characteristics of TPLT, affected by the pipe diameter, the heating power capacity, and the liquid filling ratio.

Investigation of heat transfer and flow characteristics in two-phase loop thermosyphon by visualization experiments and CFD simulations

As an efficient heat transfer device, two-phase loop thermosyphon (TPLT) has a broad application prospect in many engineering fields, and its internal gas-liquid phase change and flow characteristics are the key factors affecting the heat transfer performance. In order to get a better thermal design and performance, it is necessary to clarify the heat transfer mechanism of the TPLT, especially under the condition of high filling ratio. In this study, the visualization experiment was combined with the CFD method to study the heat transfer and flow characteristics of TPLT. Due to the strong coupling relationship among the boiling process and the condensate process, the Lee model is optimized, and the relationship between saturation temperature and local pressure, and the parameter of subcooling degree in the Lee model were both introduced to accurately simulate the phase change process. Results shows that the optimized model has good prediction performance for the heat and mass transfer simulation of the loop thermosyphon. The two-phase flow in the loop thermosyphon changes from slug flow to churn flow with the increase of heating power at low filling ratio (50%), while the bubble size decreases and the number of bubbles increases with the increase of heating power (20W-80W) at high filling ratio (70%). The heat transfer mechanism before and after model optimization has changed, from saturated flow boiling to subcooled flow boiling at high filling ratios. At low filling ratio (50%), the fluid in heating section is saturated state, and the flow velocity at the bottom of the loop is low (0.018m/s). At high filling ratio (70%), the fluid in the heating section is supercooled state, and the fluid flow velocity at the bottom of the loop is high (0.171m/s). This indicates that the heat transfer mechanism of the loop thermosyphon at low filling ratio was saturated pool boiling, and the filmwise condensation occurs in the condensation section. However, the heat transfer mechanism is subcooled flow boiling at high filling ratio, and the gas-liquid two phases in the condensation section are in a mixed state.

A compacted non-pump self-circulation spray cooling system based on dual synthetic jet referring to the principle of two-phase loop thermosyphon

A traditional spray cooling system usually requires a pump to circulate the fluid, and the kinetic energy of high-temperature steam is wasted. A two-phase loop thermosyphon (TPLT) which can circulate its working fluid is thermally driven. However, heat leakage may occur for low heating power. This paper proposes a compacted non-pump self-circulation spray cooling system named active two-phase loop thermosyphon (ATPLT). Dual synthetic jet integrated with spray cooling (DSJS) is used to enhance the performance of evaporator of ATPLT. Without an external pump, the waste heat and evaporation of liquid spray drive the system internal pressure to increase, which pumps the water to the reservoir as well as avoid heat leakage. It only needs a little working fluid and a little energy consumption for actuator, but can maintain hundreds of Watts of heat dissipation capability for a long time, which can facilitate the development of the energy systems. The performance of ATPLT is studied through temperature, pressure, laser particle size and particle image velocimetry experimental researches. The experimental results show that the cooling capability of ATPLT is mainly influenced by Re, We and Ja, and finally a correlation for ATPLT cooling is established with relative errors within ±18%.

Analysis of the heat-carrying performance of natural circulation loop using modified RELAP5/MOD3.4

Since the successful manufacture of the separate heat pipe (also known as Two-phase Loop Thermosyphon or Natural Circulation Loop), it has been used in many applications, especially for waste heat recovery/remove and cooling systems. We use the modified system analysis program RELAP5 to study the medium-sized separated heat pipe setup MSL2 built by Seok-Ho Rhi. To better calculate heat pipe performance under low pressure, we have improved a series of models, including the bubble nucleation model, the heat flux partition model, the interfacial heat transfer, the drift flux model, the wall heat transfer model, etc. Then we use the low-pressure subcooled boiling experiment to verify the modified code. The validation results show that the modified code accurately captures the subcooling boiling phenomenon under low pressure and low flow conditions. We use the modified code to investigate the factors influencing heat-carrying performance and analyze their action mechanisms. The results show that heating power, volumetric filling rate, and cooling water temperature influence heat-carrying performance. Additionally, we analyze the heat pipe operating parameters over time to obtain the characteristics of the heat pipe at various stages.

Effect of heat leakage on the operational characteristics of two-phase loop thermosyphon with a thermal insulation pipe

In this paper, a two-phase loop thermosyphon (TPLT) with a hollow polytetrafluoroethylene (PTFE) thermal insulation pipe (TIP) installed below the evaporator section was fabricated to experimentally investigate the effect of heat leakage on the TPLT performance. The startup and heat transfer characteristics of TPLT were compared and evaluated using HFE-7100 as a working fluid at volumetric filling ratios of 35–55%. Two startup modes, with and without temperature/pressure overshoot, were evidenced for the TPLT, and they were heat load dependent. The startup time of TPLT increased with the filling ratio and decreased with the power input. Owing to the hot-cold fluid interaction and mixing at the lower part of the evaporator characterized by larger temperature differences for them, it caused the evaporator temperature fluctuations, and the temperature oscillation amplitudes aggravated with the increase of filling ratio at lower power inputs. The utilization of a TIP into the TPLT increased both the thermal efficiency and thermal performance at filling ratios of 35 and 45%, while opposite results were obtained at the filling ratio of 55%. At the filling ratio of 35%, a highest thermal efficiency of 87% was achieved for the TPLT with a TIP at the power input of 90 W, which was 7.8% higher than that without a TIP. Accordingly, a maximum effective thermal conductivity of 1.5 × 105 W/(m·K) was obtained and 8.2% higher than that without a TIP. The addition of TIP lowered the heat leakage towards the liquid line, and it provides a cost-effective option to improve energy utilization and conversion efficiency for prospective applications.

Characteristics of phase-change flow and heat transfer in loop thermosyphon: Three-dimension CFD modeling and experimentation

Two-phase loop thermosyphon (TPLT) shows an oscillation phenomenon since the complex phase-change heat transfer and flow behaviors, decreases the system reliability in practice. A combined three-dimension CFD simulating/experimental investigation was carried out to investigate the phase-change flow inside TPLT. Results of the 3D-CFD model show good agreement with the experiments, with a maximum deviation of 2.86% and 3.98% for temperature distribution and pressure, respectively. In the vertical evaporator heating mode, the filling ratio of 23.3% produced the lowest total thermal resistance of 0.28–0.22K/W since the dominant heat transfer mechanism of phase-change in the loop. With the increasing FR, from 48.0 to 84.1%, the dominant heat transfer mechanism might be transformed to single-phase convection. Thermal performance with the horizontal evaporator heating mode is better than that with the vertical evaporator heating mode since the good flowability at high FR = 84.1%. In the horizontal evaporator heating mode, a bidirectional flow was observed in the loop with the horizontal evaporator even at low FR = 23.3%, which caused pressure fluctuation and reduced thermal performance. But the flow stability could increase by 90% with the auxiliary of a porous media in the horizontal evaporator, indicating that the porous media had a positive effect on avoiding bidirectional flow.

Design and Validation of Closed Two-phase Thermosyphon Loop in Lunar Gravity Environment during China Lunar Project CE-4

Design and Validation of Closed Two-phase Thermosyphon Loop in Lunar Gravity Environment during China Lunar Project CE-4

Mechanisms of dropwise condensation on aluminum coated surfaces

Dropwise condensation (DWC) is a complex phase-change phenomenon involving the formation of randomly distributed droplets on the condensing surface. The promotion of DWC instead of the traditional filmwise condensation (FWC) is a promising solution to enhance the efficiency of heat exchangers by increasing the condensation heat transfer coefficient. The interaction between the condensing fluid and the surface (wettability) is important in defining the condensation mode. On metallic surfaces widely employed in heat transfer applications, the condensing process occurs in filmwise mode. Ideally, an engineered surface designed to achieve high DWC heat transfer coefficients should present low contact angle hysteresis and low thermal resistance. Among the different available techniques to modify the surface wettability, hybrid organic-inorganic sol-gel silica coatings functionalized with hydrophobic moieties (phenyl or methyl groups) have been identified as a feasible solution to promote DWC on metallic surfaces. In the present paper, different aluminum sol-gel coated surfaces have been tested during DWC of steam in saturated conditions. The realized coatings have been characterized by means of dynamic contact angles and coating thickness measurements. Condensation tests have been performed using a two-phase thermosyphon loop operating in steady-state conditions that allows visualization of the condensation process and simultaneous heat transfer measurements. Heat transfer coefficients have been measured by varying the heat flux, at 106 °C saturation temperature and with vapor velocity equal to 2.7 m s−1. A high-speed camera is used for the visualization of the DWC process.

Experimental study on the effect of filling ratio on an R141b two-phase thermosyphon loop with a horizontal parallel tube evaporator

A two-phase thermosyphon loop is an ideal heat transfer device to achieve compact and efficient cooling with low energy consumption. In this paper, a two-phase thermosyphon loop with a horizontal parallel tube evaporator for multiple heat source cooling is proposed. The effect of the filling ratio on the transient response of temperature and pressure, heat transfer characteristics, instability issues, as well as flow regimes under different heat loads are investigated experimentally and visually. The filling ratios are divided into three groups according to their unique heat transfer and instability characteristics. The research results show that a too low or too high filling ratio is not conducive to the safe and stable operation of the system. At medium and high filling ratios, temperature and pressure overshoot are prone to occur, threatening the safe operation of the system; geyser boiling is another unstable phenomenon that can be inhibited as the heat load increases. Gravity will lead to uneven distribution of working fluid in the evaporator and further affect the temperature uniformity and heat transfer capability. From the perspective of temperature control performance and heat transfer capability, 30% is the optimal filling ratio in this study, with a minimum thermal resistance of 0.12 ℃ ⋅W-1 and a maximum heat transfer coefficient of 1345.36 W⋅m−2⋅℃−1. This paper provides a basis for designing and applying a two-phase thermosyphon loop for multiple heat source cooling in confined spaces.

Thermal performance of a two-phase loop thermosyphon with an additively manufactured evaporator

• Thermal performance and instabilities were studied for a loop thermosyphon. • The loop was examined at different powers and charges of water and ethanol. • An additively manufactured evaporator was compared to a machined counterpart. • A model was developed to explain the relation between flow rate and instabilities. • 3D-printed surface demonstrated better stability, but with higher thermal resistance. This work investigates the effects of an additively manufactured (AM) evaporator on two-phase loop thermosyphon performance. The thermosyphon employs a radially finned, air-cooled condenser connected to an aluminum side-heated evaporator by nylon tubing. Two evaporator surfaces were examined: one with smooth conventionally machined aluminum channels and the other with channels additively manufactured by selective laser melting (SLM). The loop thermal performance and the operational instabilities were characterized for different working fluid charge volumes using water and ethanol. The instabilities were quantified using the maximum fluctuation amplitude of the evaporator wall temperature. Results show that increasing the input power decreases the total resistance and lessens the corresponding instabilities. Low fluid charges result in better thermal performance and lower evaporator temperature instabilities, but they reduce the loop’s maximum heat transport capacity. The peak in condenser resistance was found to serve as a good indicator for the end of geysering. Finally, the AM evaporator resulted in slightly higher thermal resistances compared with the conventionally machined version; however, it decreased temperature fluctuations at the heat source.

Comparative Thermal Performances between Pumped Thermosyphon Loops with Different Condenser Configurations Using R245fa as Working Fluid

A pumped two-phase thermosyphon loop is broadly utilized to intensify the cooling duties of electronic chipsets/systems and the effectiveness for harvesting thermal energy. The configuration of a condenser not only affects the heat transfer in the condenser, but also has an effect on the saturation pressures during the boiling and condensation processes to alter the hydrothermal performance of a pumped thermosyphon loop. The influence of the condenser configuration on the hydrothermal performance of a pumped thermosyphon loop is rarely studied. The present study comparatively examined the thermal performances of two pumped thermosyphon loops with a conventional tube-fin condenser and the expansion-tank condenser. The thermodynamic cycles in pressure-temperature and pressure-enthalpy diagrams, Nusselt numbers of evaporator and condenser, thermal resistances and various performance indexes evaluated at constant pumping powers at the controlled through-flow Reynolds numbers, boiling numbers and condenser thermal resistances were measured. At the similar thermal loads, flow rates, and fluid entry temperatures of condenser, the operating pressure of the thermosyphon loop with expansion tank condenser was considerably reduced from that with tube fin condenser, leading to the lower saturation temperature for reducing the thermal resistance and the lesser pressure drop across the loop with a noticeable hydrothermal performance improvement. At the parametric conditions tested, the ratio of dimensionless overall thermal resistances between the loops with expansion tank condenser and tube fin condenser fell in the range of 0.81–0.99. When the loop performance was compared at a constant cooling airflow rate without considering the more pumping power consumption for the loop with tube fin condenser, the ranges of thermal resistance for the loops with expansion tank condenser and tube fin condenser were 0.13–0.21 (KW−1) and 0.15–0.23 (KW−1). The merit indices evaluating the comparative hydrothermal performances of evaporator, condenser and loop between the two looped thermosyphons highlighted the significance of condenser design and affirmed the performance improvement by changing tube fin condenser into expansion tank condenser. The empirical correlations of evaporator Nusselt number, condenser Nusselt number, and overall thermal resistance using Reynolds number, boiling number, and condenser thermal resistance as the controlling parameters were generated for relevant applications.

Experimental investigation of flow characteristics in a vertical vibration two-phase loop thermosyphon

In this paper, flow characteristics of a two-phase loop thermosyphon under vertical reciprocating vibration are visually investigated with N-pentane as the working fluid. The tests are performed for a heating power range of 20 W to 40 W, the filling ratio of 30 % to 70%, and a 30 m?s-2, 35 Hz vertical reciprocating vibration. The effect of vertical vibration on flow characteristics of the two-phase loop thermosyphon is investigated by comparing the obtained results with those acquired in static, thereby providing a basis for explaining the heat transfer process of two-phase loop thermosyphon under vibration. The results indicate that vertical vibration promotes the rupture of a liquid plug and the transformation of the plug flow to annular flow or wavy flow. Furthermore, the vertical vibration does not change the distribution law of liquid flow velocity in the two-phase loop thermosyphon. However, it will reduce the overheating and flow velocity in the two-phase loop thermosyphon at the start-up. With an increase in the heating power, the influence of vertical vibration on liquid flow velocity is reduced due to continuous disturbance of the working medium in the two-phase loop thermosyphon.

Numerical Study of the Air Conditioning of a Room by a Two-phase Thermosyphon Loop Using Meteorological Data from Mamou (Guinea)

This paper presents a numerical study of the air-conditioning of a room by a two-phase thermosyphon loop using meteorological data from the Mamou region (Guinea). The room is composed of a rectangular roof and a passenger compartment in the form of a parallelepiped. In addition, the air-conditioning unit that operates with methanol is composed of an evaporator, a condenser, a riser and a downcomer. The heat transfer modelling governing the habitat model and the air conditioning loop is based on the nodal method. The coupling of the system is done by convective transfer between the internal air of the habitat and the surface of the evaporator. The equations are solved by the implicit finite difference method. Thus, this resolution made it possible to determine the influence of the parameters on the model. This work presents results of the habitat with and without the air-conditioning loop for typical days in March of Mamou. These results show that the use of the air conditioning loop can contribute to lowering the internal air temperature. The value of the maximum temperature of the indoor air of the habitat with the air conditioner is about 299 K while that of the air without air conditioner is about 303 K. The variation of parameters such as temperature, wall thickness, incident solar flux, air exchange rate and evaporator surface has a significant impact on the operation of the air conditioner and on the temperature of the conditioned room. A low wall thickness or a high air exchange rate contributes to the temperature increase in the room. For a wall thickness of 10 cm, 15 cm or 40 cm, the air temperatures are 301.5 K, 297 K and 296.9 K respectively. However, for a habitat without an air conditioner the temperature is 303 K when the wall thickness is 15 cm.

Numerical simulation on the heat transfer characteristics of two-phase loop thermosyphon with high filling ratios

The two-phase loop thermosyphon (TPLT) with a high filling ratio is considered an efficient heat transfer device and therefore has a good application prospect in the field of high heat flux dissipation engineering. However, the heat transfer mechanism of the TPLT with high filling ratios remains elusive. In this study, we establish a computational fluid dynamics (CFD) model of the loop thermosyphon. In order to accurately simulate boiling and condensation processes, we take into account the relationship between saturation temperature and pressure in the phase change model. There were two flow patterns, i.e., the bubbly flow and the slug flow, under low filling ratios in the heating section, in which the pool boiling dominates the main heat transfer mechanism, and dropwise condensation occurred in the condensation section. The driving force to propel the liquid during the vapor bubbles rise cannot be transferred to the liquid in the right tube, resulting in lower flow velocity. In stark contrast, the single-phase flow and the bubbly flow occurred periodically in the loop thermosyphon with high filling ratios, in which the dominant heat transfer mechanism is the flow boiling. The rising bubbles promote the clockwise flow of liquid in the loop like a pump. Because of the switch of the heat transfer mechanism, the average flow velocity increased, and the thermal resistance decreased. The minimum thermal resistance was 0.15 K/W under a filling ratio of 75%, and the maximum average velocity of the fluid was 0.19 m/s. Furthermore, we found a strong coupling relationship between the heat transfer performance and the flow characteristics of the loop thermosyphon. For low filling ratios, local dry-out occurred in the loop thermosyphon under a high input heat flux, leading to an increase in the thermal resistance. For high filling ratios, the average velocity of the fluid was augmented with the increase in heating power, while the liquid was capable of being replenished quickly in the heating section to avoid the dry-out. Therefore, the loop thermosyphon with high filling ratios enables a better heat transfer performance under a high heat flux than those with low filling ratios.

Experimental parameter studies on a two-phase loop thermosyphon cooling system with R1233zd(E) and R1224yd(Z)

• Experiments on Two-phase loop thermosyphon (TPLT) studying influencing parameters. • Self-regulation compensates changes in heat load, height difference, mass flow rate. • Identification of optimal charge avoiding instabilities and critical temperatures. • Low-GWP refrigerants R1233zd(E) and R1224yd(Z) are suitable for thermosyphons. Two-phase loop thermosyphon (TPLT) is a promising technology looking at highly effective electronics cooling. Due to strong coupling between the internal and external parameters, in this study experimental tests in steady-state are carried out using R1233zd(E) and R1224yd(Z) as a working fluid to investigate the respective influences and resulting design requirements. The relationship between the governing thermal and flow equations is presented to facilitate the interpretation of the test results. The study shows a stable flow and cooling performance over a wide range of heat loads and recooling temperatures. The refrigerant charge is identified as one of the main influencing factors, with an optimum being between excessive subcooling and beginning dry-out. Both tested refrigerants lead to basically similar results, showing minor differences regarding thermal performance and system stability.

Experimental study of a novel cool-storage refrigerator with controllable two-phase loop thermosyphon

Cool storage has been considering an efficient and cost-effective means to enhance the behavior of a refrigerator. However, its drawback in temperature control of the refrigerator compartment has not received enough attention. The controllable two-phase loop thermosyphon has the prospect of solving this problem. In this study, a novel cool-storage refrigerator integrated with a controllable two-phase loop thermosyphon is built to investigate its precise temperature control capacity. The phase change material is optimized by the orthogonal experiment method. The controllable two-phase loop thermosyphon presents the optimal cooling performance for the fresh food compartment when the filling ratio is 27.0%. As the average temperature of the fresh food compartment increases, the one on–off cycle of the controllable two-phase loop thermosyphon maintains at 32.0 min, and the operation ratio varies from 86.3% to 13.6%. The temperature control accuracy can be improved from 2.1 °C to 0.6 °C and the overall time of one on-off cycle decreases from 49.8 min to 22.4 min. The operation ratio gradually increases from 7.2% to 38.6% as the ambient temperatures increase. The results demonstrate that the controllable two-phase loop thermosyphon is a feasible and effective way to improve the temperature control performance of the cool-storage refrigerator.