Heat Pump Dryer Research Articles

Analysis of an ejector-assisted flash tank vapor injection heat pump cycle with dual evaporators for dryer application

In this paper, an ejector-assisted flash tank vapor injection heat pump cycle with dual evaporators (EFVIC) for heat pump dryer applications is proposed based on a basic flash tank vapor injection heat pump cycle (FVIC). An ejector is introduced to recover the expansion work of the system, and a high temperature evaporator is added to utilize the ejector's entrainment ability to reduce the irreversible loss caused by lower temperature difference. The performance improvements of EFVIC are evaluated through energy analysis, exergy analysis and comparisons with FVIC. The results indicate that the volumetric heating capacity and heating coefficient of performance of EFVIC with R1234yf are improved by 66.99 % and 18.88 % compared with those of FVIC using R1234yf, respectively. In addition, the presented cycle achieves better exergy efficiency because the exergy destruction proportion of expansion valves in EFVIC is 75.98 % lower than that in FVIC. Furthermore, the compressor has the highest exergy destruction among all components for EFVIC, accounting for 33.22 % of the total exergy destruction, hence it has the greatest optimization potential. The advantages of the presented cycle performance reveal its energy saving characteristics and application potential in heat pump dryer.

Techno-economic analysis of a solar-assisted heat pump dryer for drying agricultural products.

Postharvest losses (PHLs) of biomaterials, such as vegetables and fruits, significantly impact food security and economic stability in developing nations. In Tanzania, PHLs are estimated to range between 30% and 40% for cereal crops and even higher for perishable crops such as fruits and vegetables. Open-sun drying (OSD) is the most extensively employed method because of its affordability and simplicity. However, OSD has several drawbacks, including difficulties in managing drying parameters, long drying times owing to adverse weather, and product contamination. The solar-assisted heat pump dryer (SAHPD) is a technology designed as an alternative solution for drying biomaterials and reducing PHL. A limited number of SAHPDs have been constructed in developing nations. Most of the works have concentrated on the performance analysis of the systems. This neglects the techno-economic assessment, which is important to provide both a quantitative and qualitative understanding of the financial viability of the technology. The present study therefore investigates the techno-economic analysis of a novel SAHPD for drying agricultural products, particularly vegetables and fruits. To determine whether the SAHPD technology is technically and economically viable, tomatoes and carrots were dried and analyzed to determine their thermal and economic performance. The results show that the initial moisture contents of tomatoes (Lycopersicum esculentum) and carrots (Daucus carota) were reduced from 93% and 88% to 10% in 11 and 12 h, respectively. The coefficient of performance (COP), drying time (DT), specific moisture extraction ration (SMER) and thermal efficiency () were found to be 3.4, 2.3 kg/h, 1.33 kg/kWh and 54.0%, respectively. The economic analysis was assessed using the annualized cost, lifecycle savings, and payback period for the dryer's life span of 15 years. The initial investment of the SAHPD was $5221.8 and the annualized cost was $1076.5. The cumulative present worth for 15 years was found to be $23,828.8 and $27,553.1 for tomatoes and carrots, respectively. The payback period for tomatoes was found to be 3 years, whereas for carrots it was 2.6 years. Based on thermal and economic performance assessment results, the developed SAHPD is technically and economically viable to be considered for further investments.

Grey Correlation Analysis of Drying Characteristics and Quality of Hypsizygus marmoreus (Crab-Flavoured Mushroom) By-Products.

The physical properties and nutritional quality of H. marmoreus by-products (HMB) dried by different methods were comprehensively evaluated by a rigorous statistical method of grey correlation analysis. The results indicated that different drying methods had significant impacts on the characteristics of HMB. Heat pump drying (HPD) was conducive to the preservation of protein and reducing sugar, and hot air drying (HAD) maintained a high content of total flavonoids. The highest fat, polysaccharide, and total phenolic contents were obtained by heated vacuum freeze-drying (H-VFD) treatment. The unheated vacuum freeze-drying (UH-VFD) treatment achieved bright colour, lacunose texture profile, and looser organization structure. The grey correlation analysis showed that UH-VFD and H-VFD had higher-weighted correlation degrees than HPD and HAD. HMB had many higher nutritional components than commodity specifications, especially protein, fat, polyphenols, and amino acids, and had potential applications in the food industry as functional foods and nutraceutical agents.

Optimized model of sludge drying characteristics based on an experimental study of thickness, temperature, and humidity

Heat pump drying is an energy-saving method for sludge drying. However, current research on sludge drying characteristics is inconsistent with the working conditions of a heat pump. To provide an energy-saving working condition for heat pump drying, the effects of temperature, relative humidity, and sludge thickness on sludge drying characteristics were comprehensively studied. Results showed that under the conditions of 2–6 mm thickness, 40 °C–60 °C temperature, and 30%–60% relative humidity, drying time decreased by 15%–25% for every 10 °C increase in temperature when thickness and relative humidity were fixed. When thickness and temperature were fixed, relative humidity decreased from 60% to 30% and drying time decreased by about 50%. When temperature and relative humidity were fixed, drying time was reduced by one-third for every 2 mm decrease in thickness. The effects of thickness, temperature, and relative humidity on the effective diffusion coefficient were fitted and exhibited a linear experimental relationship (R2 = 0.944). Based on the Midilli model, the parameters were quantitatively processed, and the model for sludge drying under low temperature conditions was optimized based on the effective diffusion coefficient. The accuracy of the simulation was similar to that of the logarithmic model. The maximum relative error between the fitting results and experimental results was 9.8%, effectively describing the drying characteristics of sludge at low temperatures.

Effect of drying air supply temperature and internal heat exchanger on performance of a novel closed-loop transcritical CO2 air source heat pump drying system

A novel closed-loop transcritical CO2 air-source heat pump drying (HPD) system with a relatively simple structure, higher drying temperature, and internal heat exchanger (IHX) for the drying of medical equipment was proposed and built. With or without the IHX in the system, the effects of different drying air supply temperatures on the performance of transcritical CO2 HPD system were studied experimentally. The results showed that the maximum drying air supply temperature (DAST) in the designed system could reach 72.9 °C. As the DAST raised, whether with or without the IHX in the system, the coefficient of heating performance (COPh), coefficient of system performance (COPsys), and specific moisture extraction rate (SMER) decreased gradually and moisture extraction rate (MER) increased continuously. When the DAST was 70 °C, COPh, COPsys, MER and SMER were respectively 3.68, 6.07, 3.27 kg/h and 1.68 kg/(kW·h) in the HPD system without the IHX, and were respectively 4.00, 6.89, 3.67 kg/h and 1.97 kg/(kW·h) in the HPD system with the IHX. In contrast, the compressor discharge pressure decreased 4.26 %–5.99 %, COPh increased 1.39 %–8.65 %, COPsys increased 1.89 %–13.57 %, MER increased 4.68 %–14.01 %, SMER increased 6.93 %–17.18 % in the HPD system with the IHX.

Application of response surface methodology for optimisation of Cornelian cherry - Capia pepper leather dried in a heat pump drying system

The heat pump drying system was optimised for cornelian cherry-capia pepper leather production development using response surface methodology. The central composite design was used to optimise the process parameters in terms of drying time, coefficient of the performance of heat pump, coefficient of the performance of the whole system, specific moisture extracted ratio, energy consumption, drying rate and colour values. The optimal condition of independent variables was obtained as a cornelian cherry pulp concentration of 47.419% and drying temperature of 33.574°C with composite desirability of 0.846. Moreover, hydroxymethylfurfural (HMF) and effective moisture diffusivity (Deff) values of all runs were analysed. HMF was not determined in cornelian cherry-capia pepper leather. Deff values of cornelian cherry-capia pepper leather were between 1.026×10-9 - 1.532×10-9 m2s-1. The drying behaviour of cornelian cherry-capia pepper leather with optimal conditions acquired with the central composite design was evaluated with seven thin-layer drying models. The statistical parameters based on R2, root mean square of error and χ2 values were determined between 0.8267 to 0.9845, 0.004087 to 0.035626 and 0.000853 to 0.066247, respectively. Page and Modified Page models were assumed to represent the heat pump drying behaviour of the cornelian cherry-capia pepper leather in thin layers compared to the other models.

Experimental study on thermal performance of a closed heat pump drying system

The compressor speed, expansion valve opening and drying temperature are critical to the thermal performance improvement and control logic optimization of the closed heat pump drying (CHPD) system. This paper investigates the effects of the three parameters on the thermal performance of the CHPD system by the single factor experiment method. According to the experimental findings, as the compressor speed of the system increased, the heating capacity grew by 11.4%, but the coefficient of performance (COP) declined by 41.3%. As the expansion valve opening of the system increased, the heating capacity and COP grew by 73.5% and 82.9%, respectively. As the drying temperature of the system rose, the heating capacity grew by 3.1%, but the COP dropped by 25.3%. It can be concluded that reducing the compressor speed and drying temperature, and increasing the expansion valve opening could effectively enhance the thermal performance of the CHPD system.

Heating performance, exergy, and economic analysis of a heat pump drying system with an independent operating ability for drying shiitake mushrooms

In response to the problems of untimely drying in place of agricultural products after harvesting, low drying temperature of open heat pump drying system and low energy utilization of closed heat pump drying system. A novel heat pump drying system is proposed, which uses a gasoline generator as the power source and an open-closed combined heat pump system equipped with a box-type drying chamber. A prototype was constructed to investigate the feasibility and heating performance of this system, and experimental studies were carried out with wet towels and shiitake mushrooms as drying objects, and the system heating performance and specific moisture extraction rate (SMER) were analyzed. The results from the wet towels experiment revealed that the drying temperature decreased by 30%–74% when the system operation mode was the dehumidifying mode (open cycle) compared with the switching of the heating/dehumidifying mode. When the air speed was increased from 2.2 m/s to 4.3 m/s, the mass of water removed increased by 39.4%. The results of the shiitake mushrooms experiment showed that the SMER were 1.19 kg/kWh, 1.18 kg/kWh and 1.05 kg/kWh for gasoline generator drive and electric drive, respectively, which is an improvement of 42%∼61% comparing with the data of other researchers. This study provides guidance for heating performance and structural optimization of a new type of heat pump drying system driven by gasoline generator.

Comparison of different drying techniques for Zanthoxylum bungeanum leaves: Changes in color, microstructure, antioxidant capacities, and volatile components

Herein, the effects of different drying methods, namely, indoor natural drying (ND), vacuum freeze drying (FD), vacuum drying (VD), hot air drying (AD), and heat-pump drying (PD) on the qualities of Zanthoxylum bungeanum leaves were investigated. The VD-treated Z. bungeanum leaves retained their original color to a greater extent. The microstructure was significantly affected by the temperature, as evidenced by scanning electron microscopy. In addition, FD, and AD both led to high and relatively similar contents of the various components, including the total phenols, flavonoids, proteins, and sugars. The strongest antioxidant capacities resulted from AD treatment, with total phenolic and flavonoid contents as high as 65.07 mg GAE/g dw and 133.2 mg RE/g dw, respectively. Moreover, 107 volatile organic compounds (VOCs) were identified using headspace solid-phase microextraction–mass spectrometry coupled with gas chromatography–mass spectrometry and classified into eight types according to their structures. The different drying methods were found to produce variations in the number and relative contents of the VOCs, which were mainly olefins and alcohols. A comprehensive evaluation of the economic value and product quality concluded that AD is the most suitable drying method for Z. bungeanum leaves, owing to its high efficiency, low cost, and good product quality.

Parametric analysis and multi-objective optimization of a heat pump dryer based on working conditions and using different refrigerants

Considering Heat pump dryers are extensively used in the food industry, evaluating and optimizing their performance can be beneficial. Therefore, a comprehensive model is presented in this study using for waste food with considerations of energy, exergy, and exergoeconomy. Several influential parameters, such as evaporator and condenser temperatures, heat pump capacity, dry and wet-basis moisture content, along with the product mass and refrigerant types, are considered in the investigation. Five environmentally-friendly refrigerants of, R134a, R1234yf, R1234ze, R717, and R152a, are used as the working fluid of the heat pump. The parametric study shows that evaporator and condenser temperatures and heat pump capacity have significant effects on the heat pump COP, exergy efficiency, drying time, and cost of dried product. Hence, assuming these four objective functions, a multi-objective optimization model based on the TOPSIS method is presented. According to this, the optimal point of the system is found at the evaporator and condenser temperatures of 10.32 °C and 69.68 °C, respectively. Results of the refrigerant analysis demonstrate that although R717 has the best energetic performance, using R1234yf results in the shortest drying time and lowest cost of dried product.

Experimental Investigation of the Performance and Sustainability Analysis of the Classical Heat Pump Dryer

Bu çalışmada klasik ısı pompalı kurutucunun deneysel olarak enerji ve ekserji tabanlı performans analizi değerlendirilmiş ve ekserji verilerine bağlı olarak sürdürülebilirlik açısından incelenmiştir. Deneysel çalışmalarda kefal havyarı olarak bilinen botarganın kurutma karakteristiği belirlenmiştir. Yapılan deneylerde botarga 40⁰C sabit sıcaklıkta yaş baza göre ortalama %50-55 nem içeriğinden %16-17 nem içeriğine düşürülünceye kadar kurutulmuştur. Çalışmanın temel amaçlarını ısı pompalı kurutucunun performans ve sürdürülebilirliğini deneysel olarak kanıtlamak ve hassas bir ürün olan botarganın kuruma davranışlarını tespit etmek şeklinde belirtmek mümkündür. Deneyler sonucunda sistemin ekserji verimliliğinin %67.28 - %78.98 aralığında değiştiği gözlemlenmiştir. Buna ek olarak yapılan kurutulmuş botarga üzerinde yapılan gıda analiz sonuçlarına göre ortalama nem ve su aktivesi değerlerinin ise sırasıyla %16.2 ve 0.7198 olduğu belirlenmiştir. Elde edilen sonuçlar ısı pompalı kurutucunun özellikle enerji ve ekserji performansı açısından oldukça verimli bir sistem olduğunu ve hassas bir ürün olan botarganın sabit sıcaklıkta zarar görmeden kurutulabileceğini açıkça ortaya koymuştur.

Recent Developments of Heat Pump Dried Agriculture Produce: An Overview of Technical and Theoretical Application

Foods are very fundamental needs for all living beings. Cereals are harvested to meet the food requirements but it is difficult to simultaneously consume all foods. India, especially lack of consciousness of post-harvest technology and management for fresh food, large economic losses. Drying is a decrease in moisture from the product and is the most important process for storing agricultural products. The drying process involves the transfer of mass and heat in order to rapidly evaporate water from the product. Food qualities such as color, flavor, and structural alterations are changed by drying, nutritional value, and physical appearance and morphology. A heat pump is a heat generating device that transmits energy from heat by absorbing a low temperature range and released to a higher temperature. The heat pump consists of an expansion valve, two heat exchangers (evaporators and condenser) and a compressor. Heat pump calibration creates a regulated drying atmosphere (temperature and humidity) to improve quality of food product with low energy consumption. The main advantages of heat pump dryers (HPD) are the ability of the heat pump to recover energy from the exhaust and the ability to independently control the temperature and humidity of the dry air. This comprehensive review was conducted to study the drying behavior of various food materials under HPD in order to obtain high quality products.

Impact of drying methods on physicochemical properties of Fritillaria hupehensis (Hubeibeimu) flours

Fritillaria hupehensis (Hubeibeimu) widely grows in the mid-western zones of China. In the present work, we investigated the physicochemical compositions, antioxidant abilities, and thermal properties of the bulbs of F. hupehensis dehydrated by heat-pump drying (HD), vacuum drying (VD), natural drying (ND), freeze drying (FD), and microwave drying (MD). Total contents of nucleosides and nucleobases in F. hupehensis flours ranged from 727.64 to 1,654.25 μg/g, and total free amino acids ranged from 88.03 to 128.21 mg/g. FD flour had high contents of total nucleosides and nucleobases, and free amino acids. MD flour had low contents of total starch, amylose, protein, nucleosides and nucleobases, and VB1 and VB2, and high levels of total phenolic content (TPC) and antioxidant abilities. Furthermore, MD flour facilitated gelatinisation, while FD flour displayed opposite trend. HD flour had high total starch content, while ND flour weakened the bitter taste due to the percentage of sweet and bitter taste of amino acids.

Thermodynamic analysis of a modified booster-assisted ejector heat pump cycle with dual condensers

This paper proposes a modified booster-assisted ejector heat pump (MBEHP) cycle with dual condensers for heat pump dryer applications. Based on a basic booster-assisted ejector heat pump (BEHP) cycle, a low-temperature condenser is introduced between the conventional condenser (i.e. high-temperature condenser) and the evaporator to realize the dual-pressure condensation that can provide heat duty at two different temperatures for heating up dryer air. In this case, improvement on cycle performance could be achieved through the use of such dual condensers in the MBEHP cycle. The benefits from the MBEHP cycle are evaluated by using the first and second laws of thermodynamics, and performance comparisons with the BEHP cycle are also presented. The results show that when R134a is used as the refrigerant, the heating coefficient of performance COPhw and COPh of MBEHP cycle under the typical operating condition increase by 50.34 % and 16.97 % compared with those of BEHP cycle, respectively. The performance of MBEHP cycle is superior to that of BEHP cycle under all given operating conditions, especially under severe operating conditions such as high condensing temperature and low evaporating temperature. In typical operating condition, the total exergy destruction of MBEHP cycle is 12.70 % lower than that of BEHP cycle, but the ejector has the maximum optimization potential. Moreover, the heating capacity Qc and the COPhw of MBEHP cycle are 42.49 % and 12.79 % higher using R1234ze(Z) than using R134a, hence R1234ze(Z) is the most suitable refrigerant to replace R134a in the MBEHP cycle among R1234yf, R1234ze(E) and R1234ze(Z).

Newly formed phenolics selectively bound to the graded polysaccharides of lychee pulp during heat pump drying using UPLC-ESI-QqQ-TOF-MS/MS

Our study investigated heat pump drying (HPD) effects on phenolic-polysaccharide adducts of three lychee pulp grades, their composition and bound phenolic contents. During HPD, the hexose content in water soluble polysaccharide (WSP) increased continuously, and the pentose and glucuronic acid contents in WSP and dilute alkali soluble pectin (ASP) together with the hexose content in ASP increased initially and then decreased due to polysaccharide hydrolases pectinase, polygalacturonase and cellulase. After HPD, the bound phenolic content in WSP, ASP and water unextractable polysaccharide (WUP) significantly increased. Protocatechualdehyde and 3,4-dihydroxybenzeneacetic acid were newly generated phenolics and the former combined with all the three polysaccharide grades, while the latter selectively combined with only WSP. During HPD, WSP and ASP surface structures were gradually broken and became loose, but WUP surface structure was a complete and rough sheet structure. Alkaline hydrolysis caused sparser, more porous surfaces of the three polysaccharide grades. The polyphenol selectivity could be related to substrate selectivity of endogenous oxidases and the type of phenolic compounds.

Modelling of heat pump drying system powered by a hybrid PV-wind-battery plant for slow-drying hardwoods

In Chile, a small sawn lumber industry producing native hardwoods co-exists with the massive radiata pine industry. Artificial drying of these hardwoods is challenging as they only tolerate low temperatures but extended drying schedules. In this work, an energy autonomous wood drying system for slow-drying hardwoods, powered by a heat pump and a hybrid non-conventional renewable energy plant, is modelled. The model was used to simulate the drying of 3 m3 of Patagonian Oak lumber in summer and winter, considering a power plant composed by 46 photovoltaic panels (175 W), a 10-kW wind turbine, 11 lithium batteries (48 V, 100 Ah), and an auxiliary unit, as power resource. Results of the simulation show that the moisture content (dry-based) of Patagonian Oak lumber can be reduced from 102 to 12 % in 30 days, with a SMER of 2.2 kgwater/kWh. In such condition, the heat pump will consume 585 kWh per m3 of dried oak, which energy demand and autonomy are secured by the hybrid power plant. In summer, the hybrid power plant can supply up to 97 % of the dryer electric demand. The 3 % difference can be supplied by an auxiliar unit. In winter, the hybrid plant can supply up to 70 % of the power demand. Therefore, the auxiliar unit must supply the 30 % additional power demand. The results indicate that the power supply generated by a hybrid power plant adjust well to the power needs of an extended artificial drying cycle, which is required for several hardwood species processed nowadays in Chile.

Numerical simulation of heat pump thin layer drying of Amaranth leaves

ABSTRACT Dried foods are higher in nutrients than their fresh counterparts. Numerical modeling, such as computational fluid dynamics (CFD), can be used to simulate the drying process and its method, thereby the effort to fine-tune the physical experimentation can be minimized considerably. In the present study, a CFD simulation model is developed based on the experimental investigation of the drying of Amaranth leaves in the CFD optimized drying chamber of a heat pump dryer (HPD). The distribution of the fluid domain and the influence of various circumstances on heat and mass transfer are investigated. In order to solve the mass transfer equation, an external model is developed in “C” language for the source term of moisture generation in the moisture transport equation and energy equation. This external model is then linked to the model using a user defined function (UDF) in the FLUENT CFD software. The calculated and measured drying temperature and moisture fraction are presented as a function of drying time. The obtained transient simulation results of the drying process are validated with the experimental results. The results of the CFD simulation are in accordance with the experimental results as per the physics of the problem. The maximum deviation between the experimental and CFD moisture-time plot is observed to be less than 8%. The difference between CFD and experimental results is attributed to temperature assumption, heat losses, and air leakage in the drying chamber. The new CFD methodology established in this study can be utilized as a generic procedure for evaluating the effectiveness of a HPD for drying various types of leaves.

Bamboo scrimber production: optimization of post-impregnation drying process using a heat pump dryer

ABSTRACT The efficient and energy-saving drying process during the production of bamboo scrimber with preserved performance remains challenging. Herein, varying post-impregnation drying temperatures and times were applied first to study the drying rate and energy consumption of impregnated bamboo bundle in a heat pump dryer. Then curing activity of phenolic resin (PF), the physical and mechanical properties of bamboo scrimber were investigated. The results showed that the drying rate was remarkably related to the drying temperature, whereas energy consumption was more dependent on drying time. Drying at 60°C using the heat pump dryer enhanced the drying efficiency by 33-67% and obtained 51-63% energy saving compared with the drying processes in enterprises. Besides, the curing activity of PF was well maintained during drying at various temperatures and times, hence satisfactory physical and mechanical properties of bamboo scrimber were achieved. As a result, drying with heat pump technology at 60°C was the optimal post-impregnation drying condition, and is applicable to practical bamboo scrimber production.

Development of drying system by using internet of things for food quality monitoring and controlling

One of the essential aspects in managing food safety is the drying, which helps to preserve food quality and extend the shelf life of food products. The temperature, relative humidity (RH), and air velocity in dryers should be carefully monitored and maintained to ensure food quality and safety during the drying process. Also, the components of heat pump dryers are at risk due to the electric current, the high temperature surrounding the condensing unit's compressor, and the high air velocity of the drying environment. These elements affect the quality of the foods being dried, and being able to communicate alerts in real-time is essential for taking precautions against hazards that can damage the dryer's internal components. Food technology's IoT-based control (IoT-BC) system with multipurpose sensors offers options for managing the post-harvest quality of leaves as they are being dried. This study set out to design and evaluates an IoT-BC system in order to remotely control, alert of imminent hazards, and monitor the microclimate parameters, including RH, temperature, and air velocity. The impacts of the created IoT-based drying system on the quality of dried leafy vegetables were also investigated utilizing a unique dryer as a case study. The results showed that the created IoT-BC system accurately maintained the drying environment, provided reliable data about the internal microclimate atmosphere of the dryer, and provided the appropriate alarm in case of an emergency and this was based on real-time data analyses. The most important quality characteristics for dried leaves were not significantly different between the IoT-based dryer and the conventional dryer dependant on drying time. Rehydration capacity decreased with the increase in the drying air temperature from 40 to 70 °C and was maximum (6.48) at 40 °C for coriander leaves and maximum (5.59) at 40 °C for Mint leaves dried in IoT based dryer. Maximum crude fibre and protein contents for mint leaves dried in an IoT-based drier were at 40 °C and were 4.97 mg/100 g and 10.62 mg/100 g, respectively. Maximum crude fibre and protein contents for coriander leaves dried in this method were 3.76 mg/100 g and 12.23 mg/100 g, respectively. The IoT based dryer kept the leaves' superior qualities throughout the drying process as a result.

From Fresh to Dried Lavender Flower: Changes in Phytochemical Profile According to Drying Method

Lavandula angustifolia Mill. is a part of the Lamiaceae family, which includes aromatic plants used in perfumery, manufactory, food, ornamental, and medicinal sectors. Both fresh and dried lavender flowers can be exploited in different ways; however, post-harvest treatments such as drying processes can help maintain the flowers’ properties for a longer period. This study analyzed fresh (F) and dried lavender flower ultrasound-assisted extracts, comparing two different drying methods, i.e., heat-pump drying (HP) and hot-air drying (HA), to assess potential differences in their effect on the phytochemical composition (total phenolic content, total anthocyanin content, and phenolic profile) and antioxidant activity (FRAP, DPPH, and ABTS assays) of flowers, focusing on three lavender selections from north-western Alps (i.e., Susa, Stura, and Tanaro). Results showed that HP-dried flowers are to be preferred over HA-dried flowers, as they contain +66.73% of phenolics and +62.2% of anthocyanins, and they have higher antioxidant activity (from 60.32% to 284.3% more according to the assay). HP-dried flowers, particularly those from the Tanaro selection, showed also higher values in the relative antioxidant capacity index (RACI) and the global antioxidant score (GAS), ranking together with the fresh flowers. Nine bioactive compounds out of thirteen were detected by means of HPLC, seven in F (caffeic acid, hyperoside, quercetin, ellagic acid, catechin, epicatechin, and dehydroascorbic acid), four in HA (ferulic acid, hyperoside, quercitrin, and epicatechin), and two in HP (caffeic acid and hyperoside). The higher temperatures used in HA probably promoted oxidative and biochemical reactions that led to the presence and increase in these compounds. However, many other phenolic compounds may contribute to the antioxidant power of lavender extracts. Overall, HP resulted in an effective and sustainable method for drying lavender flowers and may have interesting applications to obtain final products richer in bioactive compounds and antioxidant activity to be used in the functional food industry.